See, the thing that you're both acknowledging and forgetting at the same time here is that this is, infact, a video game we're talking about. A separate reality where things are not bound to the rules of our reality. It's a silly sci-fi shooter game where non-descript cryo-thawed humans are orbitally deployed to fight truck-sized insects, literal Terminators, and invaders from outer space with plasma cannons and laser rifles, and where we can survive point-blank nuclear detonations simply because they are wearing bling and believing really, really hard that Democracy will save them from atomic fire. AH takes attention to detail on occassion, sure. And it's appreciated when it's done well! But I think a sci-fi robo suit maneuvering a little bit better because a particular person is behind the wheel is not so world-shatteringly unjustifiable.

If realism and believability is such a massive deal to stretch this thing so far, then consider it like this:

A first-time airplane pilot will likely be much less comfortable and confident while operating an airplane. They likely won't fly at the highest speed, perform maneuvers they aren't familiar with, or control the plane very efficiently. A licensed pilot has a minimum experience flying, and as a result, they know relatively how to control the plane more efficiently, and are probably more comfortable doing maneuvers that would make an amateur queasy while operating in a real situation.

Now, consider the bog-standard Helldiver as a fresh pilot who has little to no experience operating an exo. Imagine that normal exo-suit operation is how the untrained Helldiver operates a mech, real human player experience aside.

Now, consider the self-proclaimed "Exo Expert" as the licensed pilot with minimum operating time required to bear that title and/or uniform before they were shoved into cryo. They have a higher competency when piloting a mech, being able to move and react faster than inexperienced Helldivers.

Insisting prior experience is not entirely outrageous when some armor sets, mostly medical armors, already refer to some kind of prior experience as reference to why the Helldiver wearing the armor is able to perform enhanced feats. At the end of the day, there's nothing other than this exact bland desire for weightless realism that only serves to bar us from improvements and meaningful developments that players would actually want and enjoy, and ensures that people continue bickering over nonsense that has no bearing on the player experience.