True, it was many many hundreds ;) I can only assume Chibnall wrote the regeneration scene not knowing how he’d get out of it, or perhaps planned for something to happen with the TARDIS but reconsidered and decided to instead lose it for awhile. Who knows. Least of the episode’s problems, but clearly Time Lords are made of hardy stuff! (I guess one could claim the regenerative activity cushioned the impact — if we can get nerdy. Tennant’s Doctor established a Time Lord can regrow limbs soon after regeneration, so maybe a similar thing was happening to protect Thirteen from fatal injury.)