I've given this new Beatles song a listen but not really liked it very much. Paul's voice sounds too old and doddery, blending with the other voices, and there is a surprisingly incongruous guitar part, that sounds like (ironically) something from a dodgy home demo.
The problem with gussying up a demo, for me, is twofold. John might have chopped and changed the lyrics, structure etc before committing to a studio recording. Secondly, a producer might have tweaked the tempo, feel, structure and turned it into a very different song. The plodding four-square spectre of Jeff Lynne haunts this track, as it does on Free as a Bird and the Wilburys stuff.
As for it being the final Beatles song, I'm a bit skeptical. With improvements in AI audio extraction, all sorts of farts and squeaks could be lifted off the Esher tapes, clashed together with George or John home demos from the '70s and served up with drum loops and perfunctory bass lines, and then spun out as new material. A bit like the ghoulish '70s Hendrix albums that married demo material with session musicians copying Jimi's style, to build ghost tracks. You could have an almost infinite stream of new Beatles tracks using the most scant original material to enfkesslyextrapolate new songs.