After ~25 years of following Apple rumors I can't believe I'm saying this, but, this is absolutely the dumbest most obviously ridiculously wrong/false/unbelievable rumor ever. Period.
Believing this for even 1 second requires you to throw away 100% of all logic and knowledge of the Mac and its market responses for the last 5-10 years and basically everything about how Apple produces products. There will never be a Mac notebook without a hardware keyboard. Apple has had well over a decade to prove onscreen keyboards can be good and they have not managed it. They took away the hardware *escape key* and that caused a near exodus from power users.
And increasingly power users are the *only* users of macs.
This is the stupidest rumor of all Apple history.
A foldable iPad? Maybe. A foldable Mac? Lol. If you buy that dumb 💩 I have a bridge to sell you.
The source of this rumor is purely supply chain based speculation and it has generated very bad rumors many times. A past rumor that aligns with this one could be the entire explanation. Fact: Apple already uses foldable displays in iPhones! And there were rumors leading up to their adoption and everyone was thinking "oooh it's gonna fold in half or in this way or that" and guess what? The entirety of the application of folding displays in iPhones is to allow the controller to be placed behind the display instead of below it. It "folds" out of view under the chassis!
This exact same use of folding display tech could be relevant to Mac notebook design, something totally invisible to users and only relevant to building the machine, maybe making it slightly smaller in one dimension or something.
Another possible reason for using this tech in Macs that is more visible could be a display equivalent of the old IBM ThinkPad butterfly keyboard (not to be confused with the catastrophically bad Mac butterfly keyboards, the response to which is further evidence that the idea of an "all screen" Mac is stupid). That is, imagine a notebook that upon opening had its display automatically fold out to a larger size than the footprint of the folded device. That wouldn't replace the keyboard or do any stupid things that will not happen (e.g. touch screen mac) but would be a cool way to begin to move to 21:9 display adoption, evidence of which is beginning to appear in Apple TV.
Of course rumors are making nonsensical claims like 21:9 support is added because "most projectors use it" which is hilariously and trivially disprovable, most projects are natively 16:9. But ultrawide displays are very popular on desktop. I suspect Apple plans to move to this display format for iMac (the rumored "large" iMac) and possibly other displays so beginning to bake in knowledge of this ratio into the software in general would align with that.
So what if they want to standardize the notebook displays on 21:9 too? A fold-out/roll-out display would be a very cool way to make that happen!
But bottom line: an all-display Mac is not happening, and it's the most trivial level of knowledge of this product and this company to know this. Every such rumor is purely a disrespectful waste of everyone's time.