I'm familiar with some parts of that team and I can say there is no capacity for development of proof-of-concepts. They are not engineers in the way you're thinking.

What does that even mean? I think it's entirely reasonable to ask if this has a chance of being adopted and supported long term (and entirely reasonable to not be particularly polite about it).

Google has a long history of abandoning products that aren't ads or search, especially messaging products. Nearly forty messaging products by my count.

I read this as “your very specific hypothesis of team structure leading to abandonware is factually incorrect” implying it’s some other team building it and therefore we have no idea how much resource is invested in this.

As a counterpoint, the DMA is requiring “Gatekeepers” like Google to enable interoperability for their messaging systems, so this protocol (or some other alternative implementation) is likely required to avert billions of dollars of fines.

Right, but abandoning projects at Google is an endemic problem. The specifics of a team are almost entirely irrelevant.

What it means is, if it is ever created, the privacy engineers will be acting in a guidance and advisory role and not actually literally building the product.