The sign editing screen no longer distinguishes between standing signs and wall signs

In release 26.1.2 and earlier, editing a wall sign would show the sign without a post, as that post does not exist for wall signs. Only editing standing signs would show the post.

As of snapshot 7, the sign post now appears regardless of whether the sign is wall mounted or not. This is incorrect and, from reading the changelog, appears to be undocumented, implying this is not an intended change.

Expected behaviour would be that of 26.1.2 and prior versions.

This is effectively to normal signs what MC-256807 is to hanging signs, and fixing both at the same time may be the better idea. Is it possible to have a rendered 3D model in the interface rather than an independent texture file? MC-261212 is also closely related.