Comment:
Can you write the code which tells you when you have the no IPv4 “thing” without trying the IPv4 thing on a network which by definition should not have the IPv4 thing where you want people not to try the IPv4 thing?
Response:
We've been here before - I don't think there is any way to write an algorithm that can differentiate between "I can see IPv4 chatter and I should join in because this network is completely IPv6 only yet" and "I can see IPv4 chatter and I shouldn't join in because this network is supposed to be IPv6 only but some other nodes don't understand that". If a key part of the algorithm is "there aren't other IPv4 nodes chattering" then you only need one device on the network to prevent everything else shutting down IPv4.