score:2
There is no minimum time requirement between submission of application electronically and interview date particularly for non-immigrant visas. What you're hearing is all anecdotal stories.
Not only does the Department of State website not mention anything like that, I know people who have applied and gone for interviews within a couple of days. Hypothetically you can submit an application today and if you get an appointment for today you can appear for your interview.
TL:DR
With immigrant visa applications it is slightly different, after your petition has been approved by USCIS, you need to hear from the consulate that you can apply for a visa before proceeding.
Back in the day 90's when applications were purely paper based, the same date you submit your application you are interviewed, admittedly that is very long ago.