Did they shut off HD1? If they didn't go back to analog, it sounds like it's just a change in programming. That's the advantage of HD Radio. You have flexibility to add and remove program streams without making significant changes to the broadcast equipment.
Nope. They just pulled the HD2 channels. WRIT HD2 had been running the “Real Oldies” format for 10 years. WKKV HD2 had been running the Breeze Soft AC format beginning in late 2018. Their sister FMs (WRNW, WMIL) still have HD2 channels for now.
The ones they shut off were PPM encoded and had some small cume, but obviously not enough to keep them up and running.
WKKV’s HD2 just had it’s software fixed to allow PAD Artist - Title to show only 2 months before shutting it off. No idea why they bothered.