I unfortunately had 2 last year colonoscopy and gastroscopy. The top one was to see why my iron levels had dropped ( bleeding from low dose aspirin ) and the other for monitoring of ulcerative colitis. Both colonoscopies had bad prep and there was retained contents in my stomach as well, the 2 problems caused by GLPs. I had had enough after doing the prep twice and decided if they missed a tiny bit of dysplasia somewhere then bad luck rather than doing it a third time. The slow gastric emptying also meant it took 7 hours to drink the 3 litres of prep solution.
The main reason they want people to stop them is so you have an empty stomach so you cannot end up with gastric contents in your lungs after they give you sleepy drugs. The official opinion on this is it is probably not needed, but you are likely better off following instructions by whoever is doing it to keep them happy. You do not want to do the prep and then have them refuse to do the proceedure because you had not stopped the GLP's as instructed.
The slowed GI motility can also cause bad prep, so enhanced prep might be a good idea, and following the dietary instructions is a good idea, maybe even fluids only for 24 hours earlier than required. Bad prep is just some poop left in the colon so they cannot see every thing perfectly.
2 weeks after stopping there is still going to 25% blood levels of tirz so stopping it for 2 weeks does not solve the problem completely.