As a wrestler I have been on both ends of the spectrum, being called for stalling and being one of the ones stalled against. I have seen many refs not call stalling when they know it is occuring, not saying it's a bad call they believe one wrestler is doing enough to be "Offensive" and the other is "Defensive" so nothing is done, although I have seen some officals in Kansas call stalling very quickly, such as the other nite in one our duals the ref would call stalling if there wasn't any action by the bottom man for 5 seconds, while the top man could sit on top for 2 minutes and do nothing and not get called.
I am a leg rider so i know how to stall on top, but i meet the criteria of not stalling by working various moves on the top, cross face, power half, guillotene etc. and just alternate the moves, usually the kid on bottom will stall, he'll flat out belly down, arms in etc. and not let you turn them, and usually they don't get called for it because i am working something it's considered defending it, one ref will call it stalling on the bottom man, and i have been called for it this year as stalling on myself because i put in a leg and the bottom guy won't move so i can do anything so i get called, but usually it turns into a stalemate.
This is one the most uncertain things about refs out there, as far as consistency on stalling calls, but i believe that many try to make it consistent but fail to do so because so many wrestlers have different styles, stalling is a very fine line between stalling and being defensive, but i guess that is to the refs discretion
Alex