Somebody pointed out that the text on the TV is actually the same size as the text used to be on the Mac--it's just that the TV is mounted too far away from the people for that scale to be the correct one. So I think maybe the Mac and the TV have successfully conspired to achieve some kind of real-space equivalence on the TV (though the Mac is now unusable by whoever is presenting since the fonts are all three times too small).
My point is less technical: when a new display device appears, the computer can't know how that image is reaching users. It could be VR goggles or it could be a jumbotron in a stadium. A better design would focus making it easier for the user to tune the scale, rather than assuming that the Mac knows best.
This was one of the issues in linux-land, that EDID info about DPI cannot be trusted.
Projectors obviously have no idea about the final DPI and TVs often lie, because same board is used across a range of models. It is the TV equivalent of "To be filled by O.E.M." .
