You've also watched the interior if the TARDIS blow up after ejecting the newly-regenerated thirteenth Doctor in Twice Upon a Time.
Despite this evidence, here is what Chris Chibnall had to say about a new TARDIS interior design at press conference at San Diego Comic Con:
"No, I didn't say that!," he said, laughing as one of his questioners stated that he mentioned that the TARDIS exploded so we will see a new one. "I said it exploded. You said we'd see a new one." Chris Chibnall then refused any more questions on the subject.
Last week, after a photo credit was published in Doctor Who Magazine, two photos depicting portions of the TARDIS interior were discovered on character and publicity stills photographer Ben Blackall's online portfolio. Those photos, along with some other character portraits and publicity stills can be found on the Facebook page for Doctor Freedom.
Just today, Doctor Who concept artist Darren Fereday tweeted this (You are only seeing the reply because the tweet was deleted. Screenshot below):
You are most welcome & thanks for all the things & things we can't talk about yet😉— Arwel Wyn Jones (@arwelwjones) August 6, 2018
So production designer Arwel Wyn Jones had a "crazy" vision for the new TARDIS interior which I assume he designed with input from Jodie Whittaker.
As for Chris Chibnall, I think a very discerning ear is required whenever he makes statements about Doctor Who.
Update:
It seems Darren Fereday was asked to delete some tweets.Fereday not only deleted his tweets which featured his own renditions of the sonic screwdriver but also deleted his tweet about Arwel Wyn Jones' "crazy vision" for new TARDIS interior design.Had to pull the plug on the artwork! Want to thank everyone who took the time to comment and who hit that like button, over a thousand hits! Love how psyched you guys are for the show and what we've done, and hope you're loving the toy. Much love x— Darren Fereday (@DarrenFereday) August 8, 2018
Perhaps one of the secrets is that, like one of the toy versions, the tip rotates.
Of course! Been sonic-ing things ever since I got it!#DoctorWho pic.twitter.com/ruBzJZajMn— Neil (@BryterMoon) August 7, 2018
Chris Chibnall said to Digital Spy:
"Secrecy is not an end in itself."
"…it's not out of a desire for secrecy, it's a desire for that moment when it goes out of people experiencing it together."I fail to see how being secretive about the mere existence of a new TARDIS interior fits with keeping the broadcasts a communal experience when an explosion already destroyed the twelfth Doctor's console room in Twice Upon a Time so it can be presumed a new one is required.
I also fail to see how drawings of a device which has already been released as a toy version and is already in the hands of fans would also be subject to the same secrecy.
It's really a shame how restricted the creative people on the production team are in sharing their enthusiasm. Even comic and concept artist Patrick Goddard was forced to delete a tweet of a drawing he created of the thirteenth Doctor's costume the day it was revealed to the public.