asuscomm.com doesn't exist in DNS server anymore since at least Saturday, Feb 22, 2025. Then even when up, I have at least 2 or 3 times a year errors trying to register new IP, and Asus router is not retrying enough, so it's left without registration. I'm moving toward to use https://github.com/RMerl/asuswrt-merlin.ng/wiki/DDNS-Sample-Scripts#duck-dns, at least for backup.
https://dns.he.net is distinct from their 6to4 IPv6, though using DDNS is a part of that service. Just what would the other worries be if they as a service disappeared?
Being honest, I have concerns about DynV6 too, since their DDNS is pretty much a free service in support of their main business.
At least if either of these were to shut up shop, a quick fix is not to hard, though getting the exact same service is harder.