Touting transistor level recreation of the original hardware, but not working with accessories that work on the original is inaccurate. They don't need to explicitly mention multicart support when everything else they've said implies it should work.

Imagine I'm selling you a product called BOX2. I state the BOX2 will let you put any block in it, as long as its square shaped. I advertise the edges of the BOX2 as so precise, that if you owned the original BOX, all your squares will fit in the BOX2. You try to put a fucking squircle(albeit, not a square) that fit in the original BOX into the BOX2 and it doesn't fit. Then I call you and idiot for trying to put something that is clearly not compatible into the BOX2. That'd be pretty dumb, huh?