Hidden object in BLOCKS

When I edit a block, and some of it is hidden and I want to end the edit, all of them disappear from the block, regardless of whether I press Yes or No.

I think I’m seeing the same behavior.

If I insert a file with a Hidden object in it into my current file, the hidden object is shown.

If I Hide the object in BlockEdit, exit, and answer yes or no, the hidden object is removed from the Block definition, but left in the file.
Running Show reveals it.
Inserting the embedded Block a second time reveals that the hidden object is not part of the embedded block definition.