The frictions we're talking about, like health insurance being tied to an employer, make things worse for families anyway - getting rid of the distortionary regulations that cause that can only be a good thing.
In some ways this could even be an argument for the cause of enshittification of everything. When everything is liminal, it somewhat directly leads to a 'get mine and go' type mindset, which in turn leads directly to enshittification, no longer term than next quarter thinking, and so on. I've always assumed the cause of this all was MBAs, and I still think it's the primary cause, but perhaps we're creating this certain from multiple directions all at once.
Here's a source, although it isn't that detailed and is more of a descriptive literature review: https://www.urban.org/sites/default/files/publication/103581...
This too: https://www.oecd.org/en/publications/2025/07/oecd-employment... - but I didn't have time to read it in detail.
I don't think anyone believes labor mobility reduces productivity.
For my little hypothesis to be incorrect you'd need to demonstrate that a company with less experienced workers (in terms of years worked at that specific company) is more productive than with more experienced workers. I think that's very improbable.