I guess it depends on what you think decided the US Military adoption of it over the other submissions
That's the question. No doubt modularity played a big role on the decision, but was it the big factor?
The Sig P320 (P250) was a relatively new comer in the market, with a rather limited amount of exposure in the "real world", as Ken Hackathorn would say; yet it was the chosen one. One suspects savings was another deciding factor. The US Army IS on a budget as everyone else, but how much, or what percentage is spent on a sidearm? In the great scheme of things, not much. In my non-expert opinion, they chose a system, not a gun.
The Sig failures-
Usually, the simplest explanation is the correct one, that's how the world works. I tend to agree that the video -likely- depicts a user error, but that's not 100% clear. An inspection of the gun and the holster would shed more light into the ND.
Sig P320s NDs have been documented for a few years now. Even when no-one has been able to replicate them, they do and continue to happen. The user-error-poor-holster mentality will go nowhere. That would be equivalent to say P320 users are a bunch of woke snowflakes, and that's not a reality. A simple explanation requires to focus on the pistol, not just the so-many users and holsters.
I agree that Glock had their fare share of issues when they came out. Back in those days the internet was limited to .gov and universities, so those issues did not get the YouTube hammering the Sig have had. Yet, every one of those problems - the 40S&W Kaboom, being the big one were fairly - and satisfactorily - remedied.
Glock kept everyone in the dark, so to speak, but the problems quickly disappeared. Today no-one but internet commandos have come forward with a reasonable failure complaint. You hear b*#&ing about the grip angle, the block feel, the capacity, etc., but safety is not a bug in the mindset of Glock users. That's a fact backed by a 40 years reality. In his own strange way, Glock listens to his customers. A simple fact missed by the Army.
Any volunteers to AIWB carry the Sig P320? I do my Glocks!
Disclaimer: I like Glocks, but I do like HK better...that's a fact