Supposedly round 1 isn't as friendly as rounds 2-3. The admissions committees have yet to see a standard for the level of applicants coming in and thus will tend to waitlist most of their early round applicants. Ideally applying in rounds 2 and 3 if you're an exceptional applicant would probably be better
Even though adcom has a pretty good idea of what level of general calibre they are looking for in successful applicants due to years of past experience, there might be yearly fluctuations (economy, demographics etc etc) or trends.
Lets assume for a moment whatever you said is right that adcom is yet to see the quality of the applicant pool in R1 and may waitlist applicants which are not super strong.
Why should that fact alone help candidates applying in R2 who are not super strong? Exceptionally strong candidates will get admitted irrespective of the round. Strong candidates have the best chance in R1, almost similar (might be slightly less) chance in R2 and clearly significantly lower chance in R3.
Candidates who are not strong dont get admitted to top business schools in huge numbers. By very definition, top schools select the best applicants to create a diverse class. At the end of the day, waitlist or not, the best combination of applicants which meets the goals of admission committee will get selected.
One should apply whenever one's application is ready. (obviously with the caveat of R3 vs next year). I dont understand whats so complex about this simple statement.