I have no doubt it was user error but M9 is the most recent snapshot, taken on 8/4, thus making it newer than anything else I had tried which sorta blows your theory out of the water.
The monthly snapshots are not necessarily the most recent v...
adb shell "idme bootmode 4000"
adb shell "idme bootmode 4002"
If both command end up in an error about idme not found you can try
adb shell nbmode
adb shell fbmode...