I used TSA pre-check at JFK T8 (AA). More pax were being sent through the "other" machine--is this taking place at other airports?
Yes. If you alarm the WTMD you are now not given another chance to go through it - it's an immediate shuffle to the AIT scanner. Plus, the random beep now means you'll likely get the scanner instead of a hand swab.
PS: The TSA line was much shorter than two weeks ago. No more regular line diversions?
Don't know about "no more," but they do seem to be reduced at the airports I've been through recently.