I am someone who was part of the PPCG beta, so I'm slightly biased towards them.
I believe that vimgolf questions should be placed at CodeGolf.SE.
While it is conceivable that such a question would be suited to CodeGolf.SE, they only have two vimgolf questions there.
A lack of vimgolf questions at CG.SE is not necessarily indicative of a lack of interest in vimgolf questions. Neither of the questions were closed, and both of them have positive scores (+1 and +8) with multiple answers for each.
To quote from the answer on Discuss.Area51
I, for one, would not like to see hard-core golfing questions where the shortest keystroke count "wins" the contest.
Hardcore code golf has it's place, and that's at CodeGolf.SE. CodeGolf was designed for code golf, and the community is more likely to respond to vimgolf questions that meet the question criteria for the website. It's unlikely that here at Vi.SE, a site aimed towards the editor, and not necessarily games involving the editor, that code golf questions will be received as well.
Now, that doesn't necessarily mean that all golf-related questions should be off-topic. There is a valid use for finding shorter ways of doing actions, allowing you to optimize your workflow, but those should not necessarily be considered golfing. These questions should be more aimed towards "how can I do this more efficiently?" than "how do I do this as quickly and dirty as possible?".