The Physical data section should always be expanded, it doesn't take up much more space an we want people to (atleast) add page numbers.
Additionally, when "eBook" is chosen as a format, the physical data section should be disabled altogether.
the exception is page numbers, however we should have a ticketbox that basically says "this edition has no page numbers"
similar to how the "no barcode" ticketbox functions in MusicBrainz
see https://musicbrainz.org/release/87049654-5869-49a1-8410-9f7627e8e467/edit