Giving out /32s ONLY in IPv6 and /20s mostly in IPv4 isn't a good policy. Sometimes people need to be globally visible without the need for such a large block, and the largest ISPs burn through them fast enough to warrant giving them much larger blocks.
Large? How large?
The only real requirement is global visibility and, with IPv4 today, it is granted to an ISP with multiple external connectivities, which is not necessarily the case with multi6.