Can you use a single thunderbolt port to power two extended displays in clamshell mode?

Looking at cables that split a thunderbolt port to two hdmi ports, they all say that for windows you can have monitors in ABC mode, i.e. both external monitors act as extended displays, but for Mac they will only work in ABB mode, that is the two external monitors will mirror each other.

I am wondering if this is still the case when the MacBook is closed. Can it then drive two extended displays from one port?

If it matters the MacBook in question is the a MacBook pro 16-inch, 2019 with AMD Radeon Pro.

I think you've confused Thunderbolt and USB-C.

The problems with these "display splitters" that work as "ABC" in Windows and "ABB" in Mac is that they're USB-C cables. They require demux functionality in software that macOS doesn't have currently.

However if you have an actual Thunderbolt cable then it is fully possible to do "ABC" with a single cable.

The MacBook Pro's lid being open or closed makes no difference at all in this.