How is Pinning vertices supposed to work?

All I have found in the User Guide is the following:
 

But this seems like a rather simplified explanation, compared to the behavior I've observed in DG.

In my own tests, it seems Pinned Vertices, only remain "fixed" when performing a "Relax" operation.  Otherwise, if you perform alignment or subsequent unwrap operations, the pinned vertices will get moved/transformed.

Is this expected/correct behavior?  And just confusing documentation?  Or is this a bug?  (2025x rev 34723 to be precise about version I am using).