One thing to notice is that 107s that sump are Twin-Cooled motors.

 

Interesting observation.

Might I go so far as to also say that almost all the M8s that sump are touring bikes? I think we have received exactly one report of a Softail sumping (correct me if I'm wrong).

I'm thinking that the original Harley bulletin said that sumping happened under high revs and heavy load. A Softail weighs around 675 pounds, give or take 25 lbs depending on model. (except for the Heritage, that's the heaviest at 728). A touring bike weighs at least 100 pounds more than the heaviest Softail, and as much as 300 pounds heavier than the lightest Softail (CVO Ultra at 944 pounds, vs. the Slim at 642). Pushing around an extra 300 pounds has got to qualify as being under heavy load, versus a bike with the same engine pushing around 300 fewer pounds.

So I would guess that there are a few reasons we're going to hear about sumping much more frequently with the Touring bikes than the Softails:
1) the Touring bikes have a heavier load to push around, and according to Harley's bulletin, heavy load is a factor.
2) there are probably way more Touring bikes on the road, given that they've been out an additional model year.
3) I think (but have no data to support) that the Touring bikes are exponentially more likely to be ridden two-up than the Softails are, especially for long distance, which will drive up the load on a 107 Touring bike substantially.

Does this mean sumping won't happen on a 107 Softail? No, of course not, it certainly might. If I'm not mistaken, we do have a report of someone who sumped a 107 Fat Bob. But it just seems that perhaps it's less likely to happen on a Softail for a number of factors as described above.