I think you should pretty much always ignore the 'calcs' and focus instead on the Authorial Intent, as best you can determine it.
'Calcs' are basically 'deconstruction,' in a way in its most pure form. Among other things, deconstruction can mean to take a work, and try and extract from it meaning that is implied, but not stated. Obviously Overwatch never explicitly says "Soldier 76 can move at Mach 180." This is a meaning someone has derived (deconstructed) from some analysis of frame counts or some shit. This speed is an implication of some visuals or some shit.
But the essence of all artistic work is communication. And to over-analyze and 'deconstruct' to this depth is to ignore this aspect. Obviously, Overwatch never intends to communicate to you that "Soldier 76 can move at Mach 180." Indeed, it probably intends to communicate to you that he is nowhere near that fast.
But what is Overwatch trying to communicate? Well, there is no great mystery here. This isn't hard to figure out. I mean, he's man-shaped and moves like a man through man-sized environments, so it makes sense to assume they probably intend for him to move at man-like speeds. Perhaps since he is in good athletic condition (perhaps 'peak athletic condition') you might call this "Captain America Speed."
"But Miz!" You object, "'man like speed' and 'Captain America Like Speed' isn't a unit of measurement! I don't know concretely how fast that is! How will I know for certain if he would beat Spiderman in a footrace?"
And yeah, it's not, and you don't. There isn't an absolute truth answer here because Overwatch isn't about how fast Solider 76 can move. And when you try and extract "truth" from means other than what the author is trying to convey, well honestly, it's pretty much a literal crap-shoot. That is, a roll of the dice. You are getting signal from noise. And so no wonder that you wind up with data that isn't very reasonable or realistic, or 'truthful.' Probably not what you want in your search for 'absolute truth' about a character.
So don't. Embrace the fact that there isn't an absolute truth here, and you can make up whatever answer you want. That's the glory of fiction! Can Soldier 76 beat Spiderman in a footrace? Obviously there is no canonical answer to this, so you tell the tale! Can the wily ways of a peak-dad-bod old-soldier out-match the overconfident hyper-agility of a teenager? Sounds like a good read!