This may have merit if your default workflow mindset was all threads are non-blocking unless an explicit "request change" action is invoked.
GitLab's unresolved threads simply comes at it from the inverse perspective of all threads are blocking unless intent to move forward is explicitly conveyed by positively marking threads resolved. If the objective is to avoid unintended merges that manifest from inattentiveness and/or poor communication, then this is clearly the safer approach that preserves accountability.
In the case of just a comment, I see any friction created there as a direct result of poor communication between collaborators; if you can't unambiguously decide whether an in-thread comment is non-blocking/unactionable, then clarity of intent wasn't clearly conveyed to begin with.
Another thing that I thought was presumptive with this "requested changes" flag is that it signals that you want to see code change, but maybe your intent is to block a merge until the PR submitter is given an opportunity to more clearly defend an implementation decision, which may or may not result in a change.
Between draft marking, unresolved threads, and approval rules[1] to safeguard against unintended merges, I struggle to see how GitLab could possibly help me more.
There's a part of me that feels like differences in value perspective are driven by what's generally effective for open distributed collaborations v. the needs of closed enterprise teams.
[1] https://docs.gitlab.com/ee/user/project/merge_requests/appro...