Ha, yeah once you research the upgraded suit, you automatically get that stat bumps. As you can tell, it's hard to know - I'm planning on making the upgraded suit look slightly different / cooler looking in the next main update. Should probably also make it so that you can hover over the stat bars and see number values.
For loading older saves (from < 0.42), you might be onto something here.....
You would think since all the tech is already unlocked that the suit upgrade would already be applied. But I just tried loading an older game, saw that everything was unlocked in v0.42.2, saved it, and checked the save data... and it looks like the suit is still at level 0.
So that's a bug. If you wanna get the suit upgrade in your older game, hit F1 and type in: unlockTech suit
You should see your Oxygen bar and stuff refill.