Not sure if you're taking the piss or just missed it but allowing build with either protocol alone is one of the genuine ideas in this joke:

> Yeah. The date notwithstanding, I do actually think we should do most of this for real.

> Maybe we don't get away with the actual deprecation and the warnings on use just yet, and maybe we won't even get away with calling the config option CONFIG_LEGACY_IP, although I would genuinely like to see us moving consistently towards saying "Legacy IP" instead of "IPv4" everywhere.

> But we should clean up the separation of CONFIG_INET and CONFIG_IPV[64] and make it possible to build with either protocol alone.