The former proposal was made by 2 members of the Go core team. And they are also in the team of the latter proposal. So, no, the first proposal wasn't good enough for the Go authors and the new proposal is in no way a guerilla attempt.

Thanks for clarification. I followed the discussion in https://go-review.googlesource.com/c/go/+/187317 loosely, thought that this is the only way to go and wasn't aware of a second investigation stream.