I think if you release no semantic versions, people (I for one) are likely to just fork and tag their own, due to the nuisance branch dependencies are when they are out of your control. Multiple forks will cause even worse issues if they show up in the same package graph.
I guess it comes down to how you want it to be used. If the preview package were just intended for experimentation like a playground, then discouraging its use as a dependency by having no versioned releases might be a good idea. But the proposal draft says,
Even though all additions go through a thorough review, there is no substitute for feedback from real-world usage in production.
If you want it used in production, then versioned releases seem pretty much necessary, even if the numbers skyrocket due to frequent breaking changes.