Yeah that might be a minor factor mate lol.
And you're still describing something that's largely useless, because you're basically picking through it for additional usable info.
Why can't we have both? Because there's absolutely no possible way for WotC to do justice to what you're describing in a single book of 256 pages (which will also inevitably have a lot of pages devoted to monsters, archetypes, lineages, probably spells and so on), which is the maximum we're getting. That's one of the key reasons I'm against what you're suggesting, this sort of multiverse cookbook, because all you'll get, is a ton of quarter-arsed junk. I've seen it plenty of times before in TT RPGs - "we covered everything in minimal detail and it was useless to everyone!". In older RPGs they'd then release actual sourcebooks for all the stuff they quarter-arsed, but WotC isn't doing that.
Also, I've never, ever seen a writer who was any good at "options and guidance on how to cook up your own brew" write for WotC. Not even once. I don't think WotC hires people who are good at writing that kind of advice - hell I don't think there are many people in RPGs who are any good at writing that kind of advice. There are huge numbers who totally incorrectly think that they are, unfortunately! And I'm sure it's one of them who'd get to write the advice section, which would (based on previous experiences, not just from WotC) be actually extremely narrow-minded, with a really limited array of ideas, some of which were clearly much more favoured than others, and none of which had much in the way of surprise, charm, or depth.
I guess what I'm saying is I want a quality book, not just a bunch of junk some dude spitballed.