Has PEMDAS a been a lie all this time?

Personally never heard of PEMDAS before this video. Seems like a straw man. He begins by evaluating 8-2+1 as 8-(2+1) and all mistakes flow from there. Where I come from -2+1 = -1. Order of evaluation between addition and subtraction doesn't matter, because it's all addition. Likewise, order between multiplication and division doesn't matter, because it's all multiplication.