Gatwa is looking to be a lovely Doctor. Warm, caring, cheerful...
I was irked by the bi-generation thing, but IF it's true I like Reddit's take on it: that 14 lives out his life resting on Earth with Donna and family (and maybe that second TARDIS doesn't even work? Forcing him to take a much needed break) and then when he dies he gets "timey wimey"d back to Unit's rooftop and becomes 15. It explains why 15 seemed so unsurprised by the turn of events, why he said along the lines of "I'm fine because YOU healed" and "it's therapy the wrong way round", and gives 15 a chance to start afresh as a new, healed, cheerful Doctor for the soft reboot without any baggage. If so I actually see it as a positive.
Could be that this bi-generation only happens when a timelord is pushed to such a level of internal torment that a second version of themselves needs to split off in a time shifted way and recover.
It's also said that all the precious incarnations retroactively bi-generated though which is weird and I'd rather not think about that.
Also someone pointed out comments made by the Toymaker that he played with the Master and made a jigsaw of the Doctor's history might possibly be interpreted as a possible Timeless Child undo.... in which case I forgive everything