I’d have thought you’d just get a gritty and ratchetty movement of the swingarm as it moves thru its curve
That is what you get, but there’s a lot of leverage and some high forces going through rear sus so you might not notice it, especially without taking the shock off and cycling the links by hand.
Knocking etc. is normally wear in bushings, usually the shock but could be at a frame pivot.
If you don’t replace bearings at the gritty stage, the next stage is something wears when they stick. If you’re lucky it’s the bearing itself (races/balls wear). If you leave it longer, the bearing can seize and the race moves in the frame/link, then you have to replace whatever the bearing’s pressed into.
Or whatever rotates in the inner race can wear too…