I think it might signal another thing too: "We're big enough, so we don't need that booster anymore".
Trello did that back then. They provided a middle tier called Gold which gave personal users all the goodies, sans the enterprise features. When they got big enough, they moved to strip it out and everybody (incl. me) were up in arms.
We've agreed in a trade-off, and then they still moved us gradually to enterprise. Now we're all using "Team of One" professional accounts with $99/yr. price tags. Trello is an enterprise platform and we're using it expensively just because we are a bunch of people who can use Kanban boards with katana-like precision for our personal projects and/or workflows.
GitLab might be doing this move to position themselves for bigger customers. Knowledgeable people can either pay, or use self-hosted versions they may think. Also, self hosted GitLab has evolved from a simple GitHub clone to a complete pipeline solution with extremely powerful functions. Even GitLab SaaS can talk with your in-house runners, so you can have an on-premise CI/CD pipeline with cloud frontend. It's kinda crazy.
Either like it or not, but you can't burn money like Microsoft + GitHub for free tier.