I do see your point, but you picked the wrong show to begin your illustration. The Whoniverse has never been internally consistent, has never had one set of rules, and has, along the way, created literally dozens of alternate futures for Earth, with different types of technology, government and so on. The only constant thing from the beginning has been the appearance of the TARDIS, and the only consistency introduced after that was the Time War. That’s the issue with time-travel — Schrodinger's cat /timey-wimey stuff— you never know which version of the past, present or future you’re going to land in! Plus your main character alters the past or future in every episode!
The argument fits Star Trek better. Unfortunately, that series has always suffered from the Curse of the Multiple Writer. This has resulted in inconsistent character arcs, random additions to the fictional ‘history’ and wild variations in story-type. The Trekverse is what is known, technically, as a ‘mess’, and the endless parades of sequels, prequels, in-betweenquels and reboots hasn’t helped. Between this, and the mass of novels, comics, fanfictions that has accumulated, there is really no clear idea of what is canon and what isn’t. No wonder fans get ratty! I just don’t bother with Trek stuff any more, there’s no point.
As to J K Rowling, there’s a world of difference between world-building, which is what Tolkien did with Middle-Earth, Straczynski with Babylon 5, and BioWare with Mass Effect, and making it up as you go along. The latter was what Rowling did, especially in the last three books when the first films were already out and she was writing under the cosh!
Proof? Try writing fanfiction in any of the above canons. Whovians rarely have a technical quibble, they’re more interested in character, and which Doctor you should have used instead of the one you did (basically, if you didn’t use Tom Baker or David Tennant, you’re in trouble!). Tolkien fans will jump all over you for the smallest infraction. With justification, because almost every detail of that world was documented by the author. Trekkies are also woefully picky and detail -immersed, but will argue violently over what is and is not canon. Babylon 5 and Mass Effect are so tightly-plotted in terms of main narrative that you have to go ‘off the grid’, with original or minor characters and off-screen scenarios/background events. Harry Potter, however, combines a large cast of minor characters, a lack of deviation from Harrys’ viewpoint, a half-sketched world and plot-holes you can drive a bus through! Fanfiction heaven!
I know because I’ve managed to create a crossover Storyverse that combines Doctor Who, Harry Potter, Marvel, Star Trek, Solomon Kane, the Phantom, Lord Peter Wimsey and WarHammer 40 000, among others (not all in the same story, you understand, but over a number of different tales in a variety of genres).
