That seems odd that they'd still put threads on the outside of the freehub body so late in time. Uniglide was long-gone from their lineup already, and it was never Shimano's practice to use other than HG cogs with STI shifters.

Perhaps even more odd is that I bought a road bike having the early 7s version of RSX (with "compact triple"), and it had an 11-24t, 7s cassette.
So it remains a mystery how that compact cassette would even fit on that supposedly-threaded freehub body. Perhaps the shop ground it down (a standard shop modification at that time) or maybe just kluged a spacer under the "compact" 11-24t cassette(???).
Does anyone else here recall what cassette size came fitted with your RSX 7s gruppo?
I can't tell from T-Mar's catalog photo.
I didn't keep that bike long enough to ever have to remove the cassette, I'd actually just bought it for a friend to ride. It was a Diamondback Expert and I still recall how particularly poor that the bike's spoke tensioning was.