In Catholicism, do the teachers more truly constitute the "church" than the hearers?

Short answer: no, it's not a fair assessment, particularly in light of what the Church itself professes.

The assertion being made is much like asserting that the Soldiers aren't really the Army, but that the Generals are. As such, it takes on the character of a false dichotomy and is a flawed premise, since the Church as it exists isn't an either-or proposition. It is a both proposition. The two bodies require each other. (I am not sure if symbiosis is the proper term here for the relationship).

1. Without the leadership, the Church would not be what it is, due explicitly to the stated Apostolic Succession as a basis of the Roman Catholic Church. (See the Creed, among other points of doctrine on that score). The Magisterium, the teaching body, operates in a continuum over time going back as far as one needs/desires to go.
2. Without the faithful, there is NO church to lead. "We are the body of Christ" is more than a metaphor, from the point of view of the Church.

Part of what makes the Church as an institution subject to such analysis is that its life lasts far beyond the lifespan of a given believer. That said, the body of believers remains, in aggregate, even as each believer is born, lives, and then dies. This has been true since the Church was founded.

The Catechism of the Catholic Church, article 752, supports the points above:

752 In Christian usage, the word "church" designates the liturgical assembly¹⁴¹ but also the local community¹⁴² or the whole universal community of believers.¹⁴³These three meanings are inseparable. "The Church" is the People that God gathers in the whole world. She exists in local communities and is made real as a liturgical, above all a Eucharistic, assembly. She draws her life from the word and the Body of Christ and so herself becomes Christ's Body.

Footnotes / citations from the Catechism is as follows:

141 1 Corinthians 11:18; ⇒ 14:19, ⇒ 28, ⇒ 34, ⇒ 35.
142 1 Corinthans 1:2; ⇒ 16:1.
143 1 Corinthians 15:9; ⇒ Galatians 1:13; ⇒ Philippians 3:6.

A recent document (Sensus Fidei in the life of the Church) likewise minimizes any distinction between these two bodies within the Church:

4. The importance of the sensus fidei in the life of the Church was strongly emphasised by the Second Vatican Council. Banishing the caricature of an active hierarchy and a passive laity, and in particular the notion of a strict separation between the teaching Church (Ecclesia docens) and the learning Church (Ecclesia discens), the council taught that all the baptised participate in their own proper way in the three offices of Christ as prophet, priest and king. In particular, it taught that Christ fulfills his prophetic office not only by means of the hierarchy but also via the laity.

Thanks are due to @MattGutting for raising the point about Sensus Fidei addressing the matter this question refers to.

For an analyst "outside the church" to assert what the church "really is" invites error. To say that "in practice" only part of the church is "really the church" is an error. The Church only exists with both.

This statement in particular is at odds with what it means to be In Communion with the rest of the Church:

but the former is adorned with them only indirectly. (5.2.A.1; bold added)

The Seven Sacraments are available to all of the Faithful, with the notable exception being that for deacons, priests, and bishops their accepting ordination will limit or preclude the Sacrament of Marriage. The Sacrament of Ordination is a calling to service and sacrifice at the individual level, for the good of the whole; the other Sacrament of Service, Marriage, is (per the church) a calling to service and sacrifice at the individual level for the good of the whole from the family on out. At this point, I am straying well into another topic / question.

Full Disclosure/Caveat: my experience with the Church is post-Vatican II. This answer relies on writings rooted in Vatican II deliberations. The conflict between what the Church now professes and the broad sweep of historical Christian thought on the point raised in the cited article in the question means that this answer is limited to current teaching. The article from which the question is derived covers quite a bit of ground. The terms in question are terms of art used in Catholic documents: ecclesia docens and ecclesia discerns can be found in John Hardon's Modern Catholic Dictionary, or in The Catholic Encyclopedia. Interestingly, the term without specification, ecclesia, has the following definition: (Per Hardon)

ECCLESIA. The unchanged Latin rendering of the Greek ekklesia, meaning assembly or community. The Bible uses the term in the Septuagint translation of the Hebrew kahal in both a secular and a religious sense. In the New Testament the word is used of the whole community of the believers in Christ (Matthew 16:18) and of a singly community of the faithful (Romans 6:5). The Catechism of Trent defines Ecclesia as the Church, which is the faithful of the whole world (I, 10,2). (Etymology. Latin ecclesia, universal or an individual Church; from Greek ekklesia, assembly of people called together.)

It is reasonable to argue that the inherent meaning in both terms remains rooted to the "single community of the faithful" and the modifiers connote roles within the greater body of the faithful aka the universal/catholic church. At this point I think I hear some angels putting on their ballet slippers ...