That's one example, and it wasn't Unity retroactively revoking a license. It was Unity clarifying that the use case (of a purchased asset by a contractor) was never part of the rights granted in the first place.

Unity's licensing model has always been that developers or users must pay for their own license (for an asset or non-free subscription) unless they are part of an entity's license. Unity clarified that only employees of an entity, or subsidiaries of an entity and the subsidiary's employees, are covered by the license.

This is generally always how it works with software licensing: independent contractors, by virtue of being separate businesses, must pay for their own tools and licenses (and indeed, that is one of the factors in the independent contractor test under federal US law).