[AccessD] Access 2021 accde (64 bit) incompatible with Access 2013 64 bit

[Ryan W]

We're upgrading to Office 2021, I made a small change to a form to fit
better with the new UI (the runtime ribbon is a bit taller for some reason)
in one of my forms which fixed the form issue for a user currently running
Access 2021.

However, users who are still on 2013 during this rollout are now getting
2467 coming out of a JIT class John Colby assisted with, and a ribbon
button that simply calls DoCmd.OpenForm "MyFormName" now errors out with a
vague message.

Literally nothing in the DB changed aside from the one form, a decompile,
compile then compact&repair and a recompile into an accde and distributed.

I've since remedied the update mechanism I use to split 2013 and 2021
accde's into different directories on the server for them to pull down and
use... but was curious if anyone had any clues?  I'm not moving across
bit-ness or any major changes, no function calls that are erroring out rely
on conversion to 64 bit (PtrSafe etc).

Shouldn't this front end still function under an older version granted I
haven't changed anything that should be a show stopper?

The form I changed isn't even the form that the errors on open reference
either....

The challenge in debugging now is that I do not have an active copy of
Access 2013 64 bit that allows for development. Only runtime environments
for 2013.