bug#51357: 26.3; Recursively copy a directory into a destination where directory already exists no longer works

[JeppeTh]

Not sure if you missunderstood. This is kind of what I want to achieve
Linux:
> cd /some/directory
> cp -rf sub_directory /tmp/
Make some changes inside sub_directory - and then copy to /tmp again
> cp -rf sub_directory /tmp/

Emacs:
M-x find-file RET /some/directory RET
Move cursor to  sub_directory
'C' and then /tmp/ RET
Will work in case /tmp/sub_directory doesn't exist.
Then press 'C' again and /tmp/ RET
Will now fail. 
Fails in emacs 27 as well.
Haven't tried emacs 25 - but works in 24.5