ORIGINAL: B.L.E.
Illegal or not, I have seen people swap crystals in 75 MHz Xmitters to get a place on the starting line of a race. No SWAT teams arrived to arrest the illegal radio fiends. It's one of those things that if it causes no problems, no one cares.
I sure do care. I don't want my 60 mph sport 40 hydro crashing into the shore or someone else's 80 mph twin outrigger crashing into the pits because someone decided they knew better than the FCC and radio manufacturers.
The licensed centers that are authorized to change frequencys probably just swap Xtals and then simply check the output to see if it's legal.
The important thing is that
they can, and do, check and if there's a problem,
they can fix it.