Didn't know what the rule is?! AYFKM? Let me guess, flag or airplane tie?
Jumpseaters preboard after the wheelchair passengers. It's in the ground ops manual. This is done so that they can make their introductions and get the f out of the way. The flight deck jumpseater is a crew member and the business select passengers have no bearing on when they board. The above comment about ground ops having disdain for pilots is spot on. I had an ops agent dress me down in front of customers in San Diego when I handed her my boarding pass stamped "deadhead" during preboards. She made it clear to me that she owns the jetway and that I don't decide when I board. I was actually embarrassed for her so I just deescalated and went about my day.
Always, even if the flight is oversold, ask the captain if it is ok if you just grab a seat. 9/10 times there is someone who doesn't show or the ops agent is keeping a secret and the flight is actually not oversold. I usually go 4 or 5 rows back and grab an aisle seat if I know it is going to be questionable, that way I can quickly make my escape up front if they need the seat and I don't have to play Tetris with the person standing in front of me who wants my seat when I need to go in front of him while he is just standing there.
The "rule" about nonrevs sitting aft of the exit row is dumb IMO. It creates headaches when the jumpseater actually has to take the jumpseat and if someone has to open that emergency exit, I would rather it be a crewmember who actually has training in doing it. Sorry if that hurts someone's feelings. A flight attendant should be overjoyed if a crewmember sits there.
When you actually nonrev it isn't an issue because you board last.
This isn't hard. Ground ops in some stations are on some sort of a power trip and I really don't get it. Most of the older and or smaller stations they are awesome.