Interesting, I've just searched and read a bit about them. E.g.
https://www.asus.com/us/support/FAQ/1039053/
Even if the 'single-pipe' bonding isn't an option for now, the more standard type could still be useful for a single device - many applications and especially game clients will open multiple connections anyway so could do in excess of 1Gbps in aggregate.
And hopefully >1Gbps Ethernet starts becoming more common as gigabit broadband rolls out! It's not like the need is limited to NAS users any more.