so I'm making the fairly safe assumption they put dummies in various different seating arrangements

The source doesn't use data from crash test dummies but from real life crashes. So we can't take seating arrangements for granted if it could meaningfully effect the numbers.

The stats apparently originate from the US government, so it's going to be a pretty big sample size that should average out any differences in seating position.

The sample size is irrelevant if cultural factors exist that could skew the results. Cultural factors like men are more commonly taxi/Uber/bus drivers, men are more likely to drive with their partner as a passenger than the inverse, etc.

I don't think there are really any conclusive after stats as the product was only introduced to the market a couple of years ago

That's a fair point, I don't expect there would be enough data for anything conclusive.

there's a correlation with male safety improving with advances in the crash test process that aren't reflected equivalently with women's safety

That would be an interesting read. I'll have a look for it.