Unfortunately Sneaky Upgrade gives some small advantages over playing vanilla even without adjusting any settings (like remembering your difficulty setting between missions), so it's not really allowed. What I mean with "not really" is that there hasn't been a solid decision made by the community yet since the game hasn't been very active.
Another reason for using the vanilla version is the load remover. Because of the massive load times it is required to submit load remover timing and it doesn't work with Sneaky from what I've tested it.
IL runs and Gold Mod runs allow the use of Sneaky. We could start a discussion about Sneaky in the Thief speedrunning Discord, and maybe add it as a modifier. That would still not solve the load remover issue.
Ok, I added your run and moved it to the new gold category. I had to edit your submission because you had the wrong YouTube link (your older run), but it should be the right one now.
For the crashing in normal Thief:DS: I had the same issue, but it only happens to me after having the game open about 1h 25mins. If I restart the game before I start and finish before that I never have any crashes.
I can add the category if you do a run of it.