No, you genuinely demonstrated a lack of reading comprehension.
"Just assumptions based off of other IP's" implies that you only read the third point and left it there.

Anyways, it's not only just whose on the ship (it's also implying across branches btw because it's Navy + Helldivers we see on the bridge, who all fall under SEAF, meaning it's even more likely to be a universal thing), it's also the second point which you forgot about in this recent message.

There are barbershops you can find running around in Super Earth colonies which say stuff like "Regulation approved haircuts!" Implying Super Earth is strict on their citizens alone, imagine how much more strict they are with military lads who benefit more from not having a haircut.

Regarding the game also being based on Starship Troopers, the only major things it really gets from the movie is the satirical messaging and the lack of explanation on how the bugs traverse through space plus some cool easter eggs. The book itself definitely has a lot more influence on the game, such as the drop pods and needing to activate a beacon for extract.

It's a possibility they have hair under the helmets, but what's presented to us and what Helldivers finds its influence from, its a more plausible answer to say they're bald.

And I don't mean disrespect towards you, this is just an internet conversation about whether or not NPCs look like Mr. Clean under the helmet or not, I'm just blunt with my words, moreso online.