Even if google doesn't use it, the collective internet applying this kind of metadata makes the web fertile for non-LLM-scraping competitors to provide an alternative option.
Rolling over to google only ensures that they remain dominant, with a high bar for competitors, and driving them to use the same technologies.
"The Semantic Web" and all related ideas were always a failure. The metadata quickly got out of date, was never correct in the first place, was only ever implemented on a teeny minority of sites, and always suffered from bad actors where the metadata didn't match the content.
Heck, even before LLMs I'd argue that Google won because they were the best at organizing vast amounts of unstructured data. With LLMs it's even more pointless to have the author generate this metadata - better to have an LLM generate it based on what visitors can actually see when they visit the site.
But when webpages die and data is accessed only by machine2machine APIs, we will no longer have this formatting for humans. Then we will need API-literate LLMs. Which means LLMs that can connect the dots between shitloads of unconnected JSONs. And if we don’t hint it for which connections are existing between that chaos of APIs, it will not be able to apply its magic. In short: we need to be able to bring JSON to vector space. And it is absolutely not meant for that, by default.
In my view, semantic web technologies should have been used to make databases interoperable, not to turn the hypertext web into an incredibly incomplete distributed database without any data quality process.
But what can you do? At this point, keeping federated alternatives, protocol-first designs, and multiple interworking implementations is more important than purity; it might well be the last successful initiative of its kind.
No, I wasn't even aware that they use anything RDF related.
And the current trend is really to connect the AI layer of Foundry with the ontology layer.
Note: after rereading your comment, I must admit that Foundry enforces data co-locality and model co-locality (==a unified centrally managed ontology). Which are NOT what the semantic web wanted.
One point to highlight about this. Open Graph succeeded more than any other web metadata proposal solely because there was obvious, immediate payoff for the website owner. That's literally the only way stuff like this ever succeeds, and then direct, clear payoff line never (and still doesn't) exist with JSON-LD.