I know that when the Conrad NYC Midtown (hilton) reflagged as a Marriott Luxury collection, it was an incredibly rushed and hasty reflag that made this Hyatt reflag look very well done in comparison. In that former case, the ownership group allegedly exited their Hilton deal overnight and very hastily penned a partnership with Marriott without the staff even knowing. The reviews did get reset, I believe, and they have been horrific there.

It is possible that Hyatt TS management knows their current state is very...erm...compromised, and wishes to keep their cache of aggregated reviews steady for now.