The Thirteenth Doctor, Jodi Whittaker

Why is Jodi Whittaker the 13th Doctor when Matt Smith was actually the 13th Doctor?

(July 23, 2018) It's firmly established that Time Lords (in Doctor Who) can have 12 regenerations, and therefore they have 13 bodies. By the accounting presented in Doctor Who, Matt Smith was Doctor #13 because his was the 12th regeneration. But, the BBC and everyone is crowing that Jodi Whittaker is Doctor #13. WTF?

Doctor #13, Jodi Whittaker, and TARDIS crew at Comic-Con 2018 San Diego

(July 21, 2018) The first public appearance of the new TARDIS crew happened this week at Comic-Con 2018 San Diego. Present were Jodi Whittaker, two of the companions, Chris Chibnal, and a Producer. They had an hour-long panel in Comic-Con, and also sat for a couple interviews with TV programs.

How will or can they explain the 13th Doctor not being in The Day of the Doctor?

(June 23, 2018) The Day of the Doctor contained the first cameo presentation of Peter Capaldi's eyebrows, and the phrase that all thirteen of the Doctors were there (Doctors 1-12 plus the War Doctor). The operative phrase being "No, sir, All Thirteen". As proper geeks our question today is, why wasn't it "All Fourteen" or "All Twenty"?