In that case, yes, that applies to GitLab too. The main problem is how GitHub and GitLab manage subprojects: GitLab forks are strictly hierarchical in how they manage pull requests and contributions (you can only submit patches from your repo to the single repo that you forked from).

But that may not be an issue for per-package repositories like Debian has on alioth. Debian does not have a monotree like the Linux kernel, every (source) package is a standalone project so the same objection does not apply here.