Yeah possibly, if they converted in the wrong direction.

There are 8 bits in a byte, so 8MB cartridges like Mario 64 were generally advertised as 64 Megabit. But if someone got mixed up they could’ve assumed the 8MB figure was actually 8Mbit and then divided by 8 to reach the wrong conclusion of 1MB.

As to why they advertised things using megabits back in the day, that’s pretty easy: bigger numbers seem more impressive in marketing!