Didn't the M1 MacBook have the much more basic issue of only supporting a single external monitor via HDMI?
This is very confusing imo
AMD's Llano (2011) supported dual/triple(1) displays on release and Trinity(2012) brought support for up to four displays at once.
(1)You could do triple displays on Llano, but it took a particular set of boards using Dual-Link DVI to drive two monitors IIRC.