I cannot speak to the various mathematical calculations made here, but I have seen some fairly practical applications of big calibre weapons. I am a recreational shooter and hunter and my round of choice is the 338 Lapua Magnum. It is simply devastating - it has a speed advantage over the .50 cal but the fifty has the weight. A quick search on YouTube will bring up several videos of big game, deer etc dropping dead as they were shot with a .50 cal. This might sound unsurprising , but in every case the round missed. The animals were not hit. The shockwave killed them - eyes ruptured and lungs trashed.
I cannot say unequivocally that this armor won’t stop a .50 cal as I have not seen it, but I would be absolutely amazed.