Absolutely, and the comparisons get kind of hairy sometimes. GS-12+ aren't all supervisory, it's possible to have GS-14 and 15s that are mostly specialists with few or no individuals in their direct charge. For those curious, the general mapping of GS grades to officer ranks:
GS-15 = O-6 (Colonel/Navy Captain)
GS-14 = O-5 (Lt Colonel/Commander)
GS-13 = O-4 (Major)
GS-12 = O-3 (Captain, this is the journeyman level for engineesr)
GS-9/11 = O-1/2 (Lt's, apprentice stage)
GS doesn't start at 9, though. The lower grades are typically limited scope, no supervisory responsibility, office jobs (secretaries, mail room, clerk, data entry, etc.). Or they're training positions, straight out of college an engineer may be a GS-5/7 and after 2-4 years a GS-11/12. They don't really have a clean comparison to military ranks, that I know of.
It gets fuzzy. Enlisted responsibility is not strictly below officer responsibility, it's just different and somewhat overlapping once you get to higher NCO ranks. A high ranked NCO could be on par with a GS-12 in terms of responsibility scope, though perhaps not in pay. I'd agree that low GS grades (say 5-9) are probably akin to E1-E4, but starting at E5 or so (AF) you start gaining responsibilities (either personnel or materiel) that are more akin, not in kind but in scope, to lower ranked officers.
GS-15 = O-6 (Colonel/Navy Captain)
GS-14 = O-5 (Lt Colonel/Commander)
GS-13 = O-4 (Major)
GS-12 = O-3 (Captain, this is the journeyman level for engineesr)
GS-9/11 = O-1/2 (Lt's, apprentice stage)
GS doesn't start at 9, though. The lower grades are typically limited scope, no supervisory responsibility, office jobs (secretaries, mail room, clerk, data entry, etc.). Or they're training positions, straight out of college an engineer may be a GS-5/7 and after 2-4 years a GS-11/12. They don't really have a clean comparison to military ranks, that I know of.