I just made a discovery that complete changes the nature of the problem: This actually has nothing to do with the U2725QE, USB4, or Thunderbolt!
The actual problem is, the FW13 AMD 7040 will hang and not POST if you have a USB pointing device connected to a daisy-chained USB hub (that is, connected to a logical USB hub that is connected (internally or externally) to another logical USB hub that is then connected to the computer.
I proved this by plugging a mouse into a plain old USB3-A hub which I then plugged into another identical hub which I then plugged into the laptop. With this configuration, the laptop didn’t POST.
The reason people are encountering it with Thunderbolt/USB4 monitors is due to the internal architecture of the monitors. They have a Thunderbolt controller (which acts as a USB hub) which is then connected internally to another USB hub that is then used to provide the regular USB ports on the monitor. This creates a logical (but not physical) daisy chain, triggering the issue when a mouse is plugged into one of the regular USB ports on the monitor. This is also why plugging the mouse into the downstream Thunderbolt port works around the issue, since that connects the mouse directly to the first hub and not the daisy-chained one.