I'm no planetary geologist (as I'm sure you'll shortly discover

) and I defer to your much greater experience on this Phil, it just appears to me to be very different to most impact craters, I'll try to explain why:
1) The dark lag deposits in the smaller craters appear evenly distributed both inside and outside the depression, and the surface appears visually very similar in age interior and exterior (similar crater sizes, and distribution).
2) The scarps are relatively bright, and fresher-looking than anywhere else on Hyperion
3) Some of the craters actually on or adjacent to the depression scarp look as if they've 'stretched' following slumping
4) The scarp is non-concentric, and in places non-existent
5) The rim is very subdued
As to the central mound, I have a wacky theory that I won't embarrass myself by airing just at the minute.....
On balance, Occam's razor no doubt applies here.
Jase