[mst]

...over-correcting distortion is at the cost of softer corners, even when you do that in software.

I'd say: especially when you do that in software.

Personally, I'd prefer to have a lens that delivers as little distortion as possible natively. At the aperture settings typically used for landscapes, border and corner sharpness is limited rather by diffraction than lens' performance. On the other hand, when shooting a subject with straight lines near the edges, less software correction is definitely welcome. But let's also be realistic: no WA natively delivers a completely distortion-free image, so if you're picky or the shot requires it, some correction needs to be done anyway. But with less native distortion to start with the correction penalty is considerably lower.

In any case: more than 8% distortion is outstanding, but not in a positive way...