My experience is that yes - if you reach Vd / Md without anything untoward happening, you declare that as Vdf / Mdf and stop. After all, if Vdf=Vd, then your airworthiness analysts did a good job.
If an aircraft is effectively speed limited and can't accelerate further - which I've seen on some small draggy aeroplanes - then we have set Vdf there. However, I can see that you might not want to do that with a part 25, and I think at that point I'd be having a robust conversation with the authority, but it is only really an issue if Vne or Mne become low enough to create a problem of margin above Vh. However, most Vh margins are relative to Vd, not Vdf.
If a TP simply didn't hit a test point but in theory could have done - then he needs to go and do it again. Irritating within a busy programme, but you may as well just bite the bullet before forced to by the authority.
G