I'm going to disagree with you. They are all more plausible, in my opinion.
And the audience thing is wrong too. They're not "in world", they, like us, are watching a comedy show. The audience in TTWAP were in show characters, so there is a difference.
Maybe I have lived with it longer, or maybe they're different enough to show the in world implausible nature of TTWAP.
No, I'd say the audience were in-world too, otherwise how would they know what Keith Hunt's catchphrase was?
KMKY was implausible from start to finish because it too, like This Time, was supposed to be a live, mainstream BBC show, there's a ton of shit that happens in that show that wouldn't fly in a real chat show. Because neither TTWAP or KMKY are real shows, they're spoofs, that's why implausible shit happens, they're not going for a facsimile representation of a chat show or The One Show, they take those formats as starting points and exaggerate them for comic effect. So no, in real life someone calling Partridge a wanker wouldn't be left in a pre-filmed clip any more than horse shit would be left on stage throughout a whole show, or a vid clip of Partridge nearly getting knocked over in Paris, or not lingering long enough on his blazer badge for him to explain it, or Partridge not knowing that the dancers were men and not women, or Partridge doing product placement (twice), or any number of other implausible in-universe moments from KMKY.
Honestly, you'll go fucking mad thinking about this stuff.