FFS! It is very simple in concept. Some versions of some songs (and many tunes if not slow airs) are done in rhythm. A such thing done in rhythm is augmented by a rhythm section that is in the right place in relation to the beat - and then it is the job of the melody people to hit the beat or be wrong.

OTOH some are not so done. Then it is the job of any drum or percussion or other "rhythm section" instrument to guess in advance where the accent is coming next, or whether silence is golden.

Getting it right in context is always a separate question.