The former change is cosmetic and inconsequential (relatively speaking, yes I know it's DNA alteration).
The latter temporarily turns you into an augment (in comparison to regular humans anyway). It's a functional rather than cosmetic difference, like making your airplane actually able to do lightspeed as opposed to just painting a starship on it. That's kind of a big deal. I'd assume the author of the Eugenics Wars books could at least understand why others would see that as a bit beyond the cosmetic DNA alterations needed to infiltrate aliens in the first episode.![]()
They're both technobabble sci-fi gimmicks employed by the very same characters. For the purposes of an exciting (if, okay, overlong) fight sequence of the sort we've seen on STAR TREK since Kirk was taking on Klingons and Gorns and Khan back in the day.
Don't really see a qualitative difference here.
Then again, I've never pretended to be a Hard-SF guy. I'm a modern-day pulp writer at heart.