I think they key thing here is that the shank of the bit shouldn’t bottom out when tightening, as that prevents further tightening. Whether that means “don’t stick out of the collet” or just “know how deep your spindle goes” is up to you.
In my router table, I dropped an O-ring into the spindle so that when I drop a bit in and tighten it, it can compress the O-ring rather than block further tightening. I wonder if a suitable rubber stop would work for Avid spindles?
I wonder, though, if imperfect collets might benefit from having the back end “loose” so the front end can be tightened further? His collet looked really beat up, and his problem might just be uneven pressure from the collet.