Hello Jordan - burning the midnight oil, eh.
i hang out in some oil forums, and some of those folks are nuts. many run Amsoil for 25K miles (with several filter changes during that interval). but they tend to get UOA's done throughout that time.
but it is insane how many miles some will run even dino oils (4-6K miles or more, often), as you commented upon. i have the exact same concerns you do: there is still blow-by, HC's and so on getting into the oil. and while the synthetic can handle it, the idea of contamination in there gets to me. im really an old-school thinker.....
since i dont do extended OCI's really (i let it go for 4 months sometimes, since sometimes it only has 200 miles on it. LOL), i did not think about the fact that you just switched over...i totally agree about getting that stuff out of there since it will have cleaned your seals. LOL. better safe than sorry. most of the time, when i first switch over, i will run a group III for a couple thousand miles to clean things up. BTW, if you have not guessed, im too lazy to do UOA's....
but most HM oils have around 15-25% group III's in them (crude generalization [M1 HM not included]- but fairly accurate, IMHO), so you probably have cleaned things up a bit already. i am gonna swap the stang over soon - are your running 15W-50 or 10-30? how is pressure vs what you ran before? im just curious....
5.0 Dom's, sorry to have chatted on your thread. i think the info is kinda interesting and pertinent to us all, IMHO. im always trying to get all the oil info and opinions i can. plus you got some bumps.

good luck.