Did you consider the S → T upgrade by this method ? One version at a time is probably safer.
I would suggest that the majority of ROMs will contain the vendor parts found in T builds, but one would be best to check by the methods mentioned at the top of the thread. [1]
With a serious backup strategy I had no hesitation in upgrading to U (testing – I cannot say more) without format data or wipe, if advising someone though I would suggest check for the presence of vendor parts first.
[1]