I saw some people with the bare minimum days, and still get their application processed within normal timelines.
Yeah.
And there is no shortage, none at all, of anecdotal reports from scores of qualified applicants suffering a processing time longer than the posted timeline, many who appear to be encountering additional processing to verify physical presence in particular.
The main reason for applying with a buffer is to reduce the risk of non-routine processing related to verifying physical presence. Not complicated.
Sure, IRCC recommends waiting to apply with a buffer to avoid the impact of falling short if an error is made. Remember, if short by even one day the application will fail. But even with a buffer applicants would be prudent to do all they can, practically, to be sure the travel history submitted is accurate. Credibility looms very large as a factor in determining which applications sail through the routine processing without significant delays versus those fully qualified applicants whose applications get bogged down sitting in long queues waiting for non-routine processing. Errors are instances in which the applicant fails to be an accurate reporter of the facts, and even though way shy of indicating misrepresentation that nonetheless will compromise the applicant's credibility . . . credibility, after all, is simply the extent to which an individual can be relied upon to be an accurate reporter of facts.
A buffer does not make the applicant more credible but it does significantly reduce the risk that the applicant fell short of the PP requirement. Lower risk PP is short, lower risk of additional inquiries to verify PP. Again, not complicated.
On the other hand, for those certain they meet the PP, odds are very good that eventually IRCC verifies that, so they do not need to wait to apply with a buffer. Other factors will likely influence how much risk there is that PP verification takes longer than the routine processing time. Whether to wait is a personal decision (would help if we knew more about IRCC internal processing guidelines, but we don't). So, it is up to the individual whether to hope to take the oath a month sooner by applying without a month's buffer, or to wait a month longer to reduce the risk of adding months, potentially many months more to how long it takes.