for those for whom it may not be obvious, the critical aspect of the
technical issue is almost certainly the question of what aaaa rrs do
to dns response message sizes. the dns directorate discussed this
many moons ago, but what notes we took were on the back of soggy beer
coasters (cooper's, i think), so i doubt that any record survived
beyond the (obsolete by the time it was published, sigh) a6 rr
discussion in rfc 3226.
I think most discussions about AAAA glue in root zone got mixed up with
AAAA for root servers, and v6 transport to root servers. So, I don't
think I ever (including DNS Directorate) have been in a discussion
where the bones are separated from the meat clearly enough.