This is key. The "SPAs can save data and improve interaction" argument is now falsifiable across a whole swath of verticals and app types.
It's natural domain is, by inspection, shockingly limited compared to its popularity.
The arguments you are making in favour of SPAs here sound great on paper - and logically they really ought to hold up - but a decade into everyone building SPAs-by-default I'm just not seeing them prove out in practice