the meaing is opposite. It means that the bug is present already in Pharo 5 so we made already a release with it and such case is probably not a showstopper. The other tag is NewInPharo6.
Just curious about the AlreadyInPharo5 tag being added to Issues you
are sorting.
For issue 14800 "AthensCanvas clipRect oddity" for example
I would guess its not in Pharo 5.