It seems to still default to v01 when I just tried.
Alternatively, some flags at the “register” action, such as --v01 , --v02 , --v02-staging as aliasses to the long “–server https://acme-v02.api.letsencrypt.org/directory” etc. could be nice.
(hmm, is that currently existing “–staging” option just an alias for the staging-v02 --server option? then I guess the last of those 3 already exists…)