I'm intending this as offering 'reasonable' explanation against PWR theory as a means of testing the latter as I find it is all too often rebutted by theories weirder than itself!
In brief, the evidence for PID/PWR seems to congeal around Paul's public 'disappearance' in Oct 1966 with all of the clues not initially taking account of this being reinforced by it.
So what exactly is involved?
Well...in THIS version, The Beatles have just stopped touring so it's a bit like retirement (as Paul "accurately predicted" a couple of years earlier in an interview with David Frost), the details of which involve George with Indian adventures when he's not in the stockbroker belt painting his house and dropping acid with John and Ringo nearby in 'wedded bliss'.
In contrast, Paul has just aborted 'family life' with the Ashers (not necessarily because he was fearing Tavistock programming but who knows?) for independent London life in his own new cavendish gaff, which rapidly becomes 'open house' to the counter-culture. He's sneakily doing coke (not telling the other Beatles) and by all accounts is out every night all night when Jane's not around, meeting everybody from Bertrand Russell to Antonioni, Joe Orton, Andy Warhol and funding varied activisms centred on burgeoning alternative culture. This is a busy boy, burning calories to a degree that soon leave his 'puppy fat' more than well behind to the degree that people are saying he looks ill. His activities, meanwhile, consorting with addicts, homosexuals and longhair activists (whom he is disposed to defend if not promote), if publicised indiscriminately, would undoubtedly have lead him to be the FIRST busted Beatle. So it's lucky he's smarter than that.
Alongside all of this 'about town', he's got an Aston Martin in which he's fond of collecting speeding tickets when his charm isn't sufficient to dissuade them and he's reported as fond of getting back up to Liverpool to hang out with his dad, his brother and varied other friends he's not quite lost contact with during the moptop years (in fact he's the Beatle who's never left Liverpool for long). Besides that, he's also known for getting up to Scotland and until the later 70's this is only rarely by plane.
If this weren't a varied enough set of new pursuits, he's also been developing a penchant for disguises via which he can be 'back as he was' before Beatledom; one of these is his specs and moustache 'trainspotter' look which readily adapts to 'photographer' and 'writer' when he fancies some action abroad in France or Spain or Africa.
There's a certain exhaustion too...and it centres on the 'comedown' from Moptop. The distractions and new pursuits leave the question unanswered 'What shall we do now?' and Paul, fearing that John and George might just as well go for 'Split up' at this point, is staying off that question, thereby encouraging him to cut his customary regular generous allotment of his time to roving reporters for he fears that all they want to do is 'prove' the Beatles are finished.
Now.....given the transforming power of new routine, new pursuits and interests and a general period of wide experimentation that is Macca's 1966 life (anticipating the 'formal' experimentation in the next albums), not to mention the transforming power of all-nighters, coke, weed, LSD and even a spot of heroin according to McCartney's most recent drug confessions (now perhaps a decade old), thr question then is:
WHAT PART OF THE ABOVE DOES NOT EXPLAIN "THE NEW PAUL" THAT EVERYONE IS NOW SAYING THEY NOTICED BACK THEN?
