I'm not sure if it's there in TOS 3.06, but the patch does not change a thing.The presence or not of this new kbdvec vector could probably easily seen with a quick disassembly of the ACIA vector for TOS 3.06.
I can't: I would not even know what to look for.
My original idea was to generate a fake key release, it had been implemented in the patch you have committed. I have no further idea, except hardcoding the address of that boolean variable for all TOS versions into FreeMiNT :-(
Would be nice to have this "feature" removed, but it is only a real issue for me on aranym, so it has not the highest priority.
-- Helmut Karlowski