If there's no law to prevent it, "traditional" cars will also soon come with unskippable ads. At least, that's the way how "traditional" TV manufacturers went. And if there is a law against it, Google or VW isn't a meaningful distinction anymore.

Nothing will stop someone from building a SDC that doesn't have the ability to be locked out like that.

The tech to do this is getting easier each year.

I think you’re assuming (incorrectly) that Google will have a monopoly on SDC technology. There are already many big players in the space, so the profit maximizing strategy is probably much closer to what the consumer actually wants.

It doesn’t seem to me like there’s a big competitive moat other than $xxb in R&D costs, so if there is unmet consumer demand for self-owned SDC, it’s probably safe to assume someone will cough up the R&D costs.

Google or someone they partner with will likely be an option. Another will be Cruise or whoever they partner with. Or, Tesla.