I guess I was more asking why a magnified ACOG over something like a red dot or halo given the bull pups more close quarter engagement usage and lower typical MOA.
A 3-4x optic kinda has the best of both worlds, enough zoom to engage targets at range and given it has a 16" barrel and shoots a .308 this is a very good thing. Also, the way an ACOG works it is almost like a dot sight works, as long as you mount it properly the red-lit aim point is very easy to see, and always in focus. so as long as your head placement is proper (and that is a requirement for dots or even irons, but not halos) If you are shooting within 10-20m you look over the top of the gun and as long as you are not blind you should be able to hit a target. If I really feel it is needed I will add an angled rds.
As for your bullpup comment, you are wrong, it is a stigma they have, but not really true as far as modern firearms go, in fact, the M-Tar has a better effective range than the M4s. A military M4 has an MOA of ~4 using 855 ball ammo (yes it really is that bad). Desert Tech is known for their accurate guns, and the MDR is no exception (see video below) shooting a 1-2 MOA, and even a sup 1 with high-grade ammo.
Last bullpups are not "close quarter engagement" they are shortened to help with that, however, they also have longer barrels than most classic rifles, and to top this off the MDR fee floats the barrel (as much as you can with a gas system) the M4 I used in the army had a 14.5in barrel and a 33in (stock extended) overall length. My MDR has a 16in barrel and a total length of 26in. so yes it helps you use it in tight spaces but if properly made does not affect its range.
MDR test at 100 yards with multiple ammo types