i can't speak for anybody but me. when i use spray baste, all 3 layers do generally stay stuck together. however, the process of rolling, unrolling, and re-rolling does disturb things a bit.
i get my best results when i take the time to re-smooth the back and smooth/pat the front [back into] place each time i get ready to do the next stage of quilting. since i'm mostly a ditch-stitcher, i re-smooth before each new line of quilting.
is that necessary? i couldn't swear to a "yes" or a "no". it's what i do when i want to be sure things will turn out as planned.
even that extra work beats the heck outta basting the whole thing first.