I'd say it's pretty true for all woofers, but yes, I do understand the point you're making. The best woofers (the exceptions) do have less distortion at high excursions than lesser woofers at lesser excursions.
But when you consider similar motor quality, then well, I seriously doubt an SDX-10, for example, will have the same distortion at 100db at 35hz as an SDX-15
- point is - bigger is not just about the max output. I don't know if, even at 90db, that a 8W7 would have as low distortion as LMS-5400.
My post earlier was general. Of course I'm well aware of exceptions / no iron rule - but I still lean towards more surface area regardless.
Surface area aside, I also think bigger boxes are better. I don't think boxes should suffocate drivers and then be compensated by EQ / watts
I'm still waiting on some measurements of the Legend or Empire. They look pretty capable for sealed subs.