I understand this rationale, and I think that as long as a CLI option is provided to go in the other direction, it seems like an acceptable solution.
In the meantime could someone confirm that the query posted by @hishammalik is a safe, correct and complete way to manually convert a private group into a public channel?
update channels set type = 'P' where name = 'channelname'
All our groups were created as private as we occasionally have guest users which should only be able to access specific channels. Once single-channel guest accounts are implemented we will want to migrate these private channels to being public.