[Dagger2]

That is also not accurate. Clients query both the A and AAAA records simultaneously up front, sort the replies according to the RFC3484/6724 rules, and then try each address in turn.

The rules are somewhat involved but they roughly boil down to "sort v6 addresses first if the client has a non-ULA v6 address, otherwise sort v4 first". However, note that the very first rule in 6177 is "avoid unusable destinations" so not having a route to an IP may factor in to the sorting.

A machine with no v6 will(/may) still query AAAA records, but it will attempt to connect to any A records first before trying any AAAA records. (This sometimes exhibits as people seeing software like apt-get report connection failures to v6 addresses and then blaming v6 for it, even though the problem is that they only have v4 and the v4 is broken.)