GitHub (annoyingly) can't do fast-forward merges from non-squashed PRs either.
Display merge request status for builds on Jenkins CI
GitLab implements basically the same API as GitHub for updating build status of commits from external services, or do I misunderstand what feature you mean?
But in general I agree, there are some options GitLab reserved for EE that really feel like they should be part of the CE as well.
And FWIW, I admire GitLab for their open source work. I just think it's worth distinguishing that it's not entirely open source.
When googling for the fast-forward feature one of the top results was this GitHub thread, which had quite a bit of activity fairly recently: https://github.com/gitlabhq/gitlabhq/issues/2324
It seems like many posting there are not aware that this repository/bug tracker is not an official channel anymore -> maybe posting an automated comment in all issues with recent activity or locking them could help avoid confusion? If you arrive via search, you don't see the notice in the main repository description.