I think I at least agree with the direction your thesis points at. None of the things you mention--rules or prep or ephemera--matter if they never arise in play; and at least in principle the point of all of them is shape the experience of play to be what the creators (the people who write the rules, the people who make the handouts, the people who prep the sessions) want it to be. Obviously, people will want different experiences of play, and even people who want the same might see (or prefer) different ways to get to them; your absolutist thesis doesn't seem to me to point to one-way-ism, in other words.
prep that doesn't get used in play can still affect play. The encounter I ran last sunday was enabled because I prepped two paths, and the players picked one... but the other path ruled out how I handled the chosen path. If I hadn't had the male bandits on the main path, the female Hare clan jizamurai on the second wouldn't be jizamurai.
The dual prep resulted in two different encounters and which was used was by player choice, but the prep itself had impacts upon other prep.
Whenever I had cool superhero character ideas, I built them in Champions (now Hero System) for literal decades after the last time I played. I enjoyed doing so. Can "play" only happen at the table, or can there be mini-games like character-creation/advancement that happen away from the table.
Traveller states so in the 1981 version. Character Gen is a minigame. Subsector gen is a minigame, too, but one without significant participant input in the "game" portion.
If 'play' includes chargen and GM prep then the OP becomes meaningless. So no, I don't think these things are 'play'.
Did you play D&D yesterday soviet? "Yes, by which I mean I sat alone and read a book". Nonsense.
Reading the book and doing prep can be different things.
For example, star system generation in Traveller, Space Opera, Alternity, and a dozen other games is presented as a minigame (often low-to-no input, hence fully automatable), then followed by an interpretive step. I'd argue that both the rolling and interpretive portions are a form of play even tho' they're solo activities, in ways very different from just reading the rules.
Similarly so for interactive lifepath generation of characters (such as in Traveller {CT, MT, TNE, T4, T5, MGT1, MGT2, T20}, T2K (2, 2.2, & 4th's optional), FGU's
Space Opera, FASA
Star Trek: The Role-Playing Game, 2d20
Star Trek Adventures and
Captain's Log) in ways that GURPS or Hero character gen isn't. They're games with player input, rolls affecting the outcomes, decisions being made, and the choices matter to shaping the outcome. (In CT, whether to continue and which skill tables are used. In STRPG and STA, which skills get raised or specializations added from the random assignments. In T2K 2/2.2/4, which skills get raised during the term.)
I've spent MANY hours doing character gen for Traveller in various editions; I don't consider it not-play just because we're doing it outside of a multi-player session. I don't consider the automation time I took for generating a whole freaking regiment for MegaTraveller (MT) to be play - but it definitely saved me a bunch of time. 1000 characters makes a lot of rolling into a few minutes of formatting output
In the 2000's (the 00's) a guy retired from the British Army as a 40-year private. He did his job, did it well, never showed leadership, but was allowed to continue to serve until retirement. Not all services exercise the
Peter Principle and of the traveller editions, only Mongoose does.
Note that a 70 year old private cannot happen in MGT due to promotion and retention being on the same roll... 70-18= 52 years= 13 terms - rare, but doable... but the support arm (the slowest promoting in MGT 1) has a promotion of 7+, and with worst case edu, needs a 9+, but to be retained he''s had to roll terms plus, so at 70, he'll have been promoted at least in terms 9, 10, 11, and 12... but he could be an ensign commissioned in term 12... or a buck sergeant. It's one of the things I bitched about in playtest as "Unlike CT/MT/TNE/T4"...