score:4
The page you linked state
Tips
If you need to have an x-ray or medical examination after you apply online, we’ll send you an email explaining what to do.
If you apply for a 23 month visa, you must provide medical certificates, unless you > have sent them to us with another application and they were issued in the last 36 months.
The Medical requirements for a WHV, state:
United Kingdom and Canada
If you are outside New Zealand and applying for a UK or Canada Working Holiday Visa for the maximum period of 23 months you must have a chest x-ray and general medical examination.
If you apply for a 23-month visa, you must provide a General Medical Certificate.
This means that it's either compulsory (for a 23-month visa), or discretionary (for shorter visas)
A General Medical Certificate (INZ 1007) (along with other forms), which is usually to be sent electronically by a INZ panel physician who you must seek if one is present in your country (if there aren't any panel physicians in your country the relevant forms can be mailed by another physician)
The Health Requirements for visa applicants are given in the form of Health Requirements for entry to New Zealand (INZ 1121) which you can check for yourself