This seemed to be related to T6831 but here we have the case of different keys and not just different subkeys.

I applied your patch and also fixed another possible problem.

Bug is in 2.2, too.

Fixed in rG591a53d716aa: gpg: Don't call keybox_compress when KEYDB_RESOURCE_FLAG_READONLY..

I found that the warning is emitted when it tries to call keybox_compress.
It should not be called when it's READONLY (which gpgv specifies).

i am not the original owner of this bug, but facing the same issue.

It would be good to apply this to 2.2, so adding "backport" tag.

One use case that seems sensible to me is to try to convince a long-running operation (e.g. a sequence of key generations) to all use a single timestamp. In this scenario, there's no interest in setting the clock to be some variant of the current time, just an interest in it remaining fixed across all the operations.

GnuPG 2.2 and 2.4 now have --pcsc-shared option for a user who can control his action in detail.
So, closing this bug report.