Seems like the above 80Hz material requires more voltage after the split, ergo, a more "powerful" amplifier is needed.
(I'm so wrong...)
I think you are thinking BlueMelon did Upper Graph=Full Range and Lower is above 80Hz.
Upper is 80 hz and lower. Lower is everything above 80 hz.
But I think they did Upper is below 80hz and Lower is above 80hz
The idea would be if they were equal, half of the power is needed for either of them e.g. only half power amp for 80hz and up.
I'm going to go down some quick assumption rabbit holes that I haven't full explored, but I think intuitively I'm on the right track.
Of course most (logical, science based) people don't want to spend more than they need to. But if one is ok with class D (should be), those watts are cheap and incrementally very chap. I don't see much reason to get let's say something based on a Hypex NC122 over a NC252. For most people the NC122 would probably be enough for these speakers but maybe not enough for their next speakers that may be much more power hungry. The NC252 would probably be enough for speakers that 90%+ of even people on here end up with. For example at March Audio the NC122=$725, NC252=$895 and NC502=$1075. Only $170 more to probably future proof your amp from a power perspective. If you end up with a huge space with some monsters you probably have enough money to eat cost of that NC252 at that point or re-purpose/sell it and get something bigger like a pair of NC1200s or NC2sk. There is also a possibility that we are seeing commoditization of clean powerful amps right now with these products. So it's also possible that 5 or 10 years later that equivalent to the NC252 or larger cost much less than now in relative dollars. Now if one feels they want or need a more expensive amp topology that might be a different story.
If they only target is amps for zones at the lowest cost possible, I think there are cheaper ways to do it. I've been going down this rabbit hole right now planning my new surround sound system and 2 other zones.