Warbler says :

Is it?

I suggest you watch the Brain Of Morbius sequence again to get the actual intention of the scene and listen to the what the Eleventh Doctor says in the trailer.

Doctor 11 : I've had many faces. Many lives. I don't admit to all of them. There's one life I've tried very hard to forget.

Note, not one of them but all of them suggesting that the Warrior isn't the only incarnation that he hasn't told anyone about and doesn't count as The Doctor.

The other incarnations being Morbius is a bit of fanon invented after The Deadly Assassin added the 13 incarnations rule (like Leia remembering Padme through the Force despite being a baby) but it doesn't make sense in the context of the mind battle and what Morbius says to the Doctor while those faces appear.

Morbius : How far Doctor, how long have you lived?

This little scene on the same planet makes sense of it all.

The Doctor isn't just any Time Lord he can and could always regenerate more than 13 times.

Indeed you could argue (with as much validity and more sense than the Morbius Doctors being Morbius) that the need for the Watcher when becoming Peter Davison and the sense of impending final death when becoming Colin Baker could be the Doctor being unsure if he can go beyond body number 13.

Indeed the Master himself who introduced this problem has regenerated at least 14 times even if you exclude all the times he was walking around wearing someone else's corpse.

Warbler said :

when/how did the Valeyard do this? I think one could argue that the time scope could only pick up past incarnations and not future ones.

The Valeyard didn't do it the Time Lords did when they scooped up the potential future Doctor from the swirl of the future and offered him the Doctor's remaining incarnations.

It proves Borusa could have picked up future incarnations but he didn't (a wise choice when it comes to some incarnations).