I cannot say much in relation to that specific video (i haven't watched it) but people have posted up some of his stuff before and from what I've seen he's not very convinving

He ignores lots of basic facts, for example in one video he claims that the overhand grip has a shorter reach becuase you need to hold the spear in the middle, completely ingoring the fact that Hoplite spears had counterweights to solve this exact problem.

The main problem with theories is that vast majority of ancient depictions of Hoplites show them using the overhand grip, he says this is due to "artistic license" which is a very weak argument given the tens or hundreds of thousands of depictions that have been found.