Just saw a discussion about this on Discord. I don’t think everyone will feel drawn to using a plug-in to achieve what, in my view, would be expected core behaviour.
I expect there is a good reason for why unlinked mentions aren’t picked up when they appear in Properties, but I think for the feature to be robust, this should be looked at.
Edit: To elaborate, not everyone will automatically link every value entered into a property. It feels a bit more manageable (perhaps just for me) to link something only when it is needed, rather than in anticipation of a need. In my opinion, this is really a strength of unlinked mentions and where this feature shines. I didn’t know I wanted to link X five months ago, but now I wish I had—enter unlinked mentions.
Unlinked mentions should therefore not only appear, but be linkable via clicking the button as usual, whether the mention is in the body of a note or in a property.