People use Lego to refer to a Lego block. So one Lego block = Lego. Two or more Lego blocks = Legos.
But you already knew that.
Yeah, I refer to 'em that way as well. One Lego block = Lego. Multiple blocks/pieces = Legos. Mostly 'cause I'm too lazy (or American, whatever) to say/type LEGO (all caps, technically) blocks. --- I hear the cackles of the crowd; they're laughing at us. And we haven't even gotten to the part where it's a joke.