Viewing distance is not necessarily a myth. For really gigantic prints that are meant to hang on the wall of a big auditorium or transit station or whatever, of course you are going to be seeing them from farther away, so it makes sense that they can have grain up close.
I sometimes think maybe we should speak more in terms of angular view than actual size, but I'm sure that would be confusing.
For prints meant to hang on home walls or gallery walls or such, sure you can make a 40x60 print from 35mm. You can also hang an outboard engine on a bathtub and call it a motorboat and if you plug the drain carefully it will probably even work, after a fashion.