
Other mistake: After the Doctor regenerates, there's a close-up of the Thirteenth Doctor's eye with the console room reflected in it. The reflection is the same orientation as a shot from behind her immediately prior, which should not be the case. Take note of the positions of the door and time rotor in both shots. (01:00:45)
Chosen answer: 1) When Stephen Moffat took over he ignored a lot of what had been developed before (there is not in-universe answer). 2) It would have killed Rose, so the Doctor absorbed the energy. His body regenerated before the energy could do a significant amount of damage that would prevent regeneration.