I've tried & failed to get that 3rd torx screw loosened, way down the rabbit's hole. I assume if I purchase the right tool, I could loosen the bastard ... but will it release the headlight in full? TIA.

2007 BPU RS4

You will need to remove the whole bumper to take out the headlights.....

x2 with the right tools and some help, it comes off in 30-45mn.

You will need to remove the whole bumper to take out the headlights.....

if you need to remove both at the same time is easier removing the bumper
if you need to remove only one, is faster by just loosening one side

So to confirm:
Even if one has success loosening that 3rd torx screw ... the headlight still does not release? What then is the purpose of the three-bolt pattern? What is keeping it connected at that point?