@mariusor It is preferable. Though I can't imagine how a client can determine what the user wants to view.
For example, if someone from InstanceA running Firefish wants to view my Pixelfed, but I have other software running behind it.
It will probably require all existing software to add an interface to let the user select.
It's probably a good first step to implement the basic, one software for one custom WebFinger. As to what happens if the user migrates to a different software…
But, as an end-user, it is also more manageable for me to have a 1:1 setup. Like in my examples, @-photos.youronly.one for my Pixelfed and @-reading.youronly.one for my BookWyrm, and so on.
(Hopefully I understood your reply correctly. ^_^:)