This is the problem of Google, or almost every other big techs. Its infrastructures, products and businesses are designed to serve at least hundreds of millions of users. This works really well for established products but significantly elevates the launch bar for new products, even seemingly easy projects like "why not having this as a small experimental website?". I won't be surprised if someone in the research team actually tried to bring up a small demo site but immediately found a showstopper from product counsels or internal AI guidelines...

Launching a full-fledged paid product is even harder, I guess you'll need to secure at least 3~40 headcounts just to integrate this into many subsystems inside Google. And this needs some senior executives driving the project since this is a cross-organization project between research and products. This creates a structural problem, in that they usually expect bigger impacts from these kind of projects to justify the cost. It's possible to pursue without involving top-down decision makers, but usually that kinds of project tends to fail to create consensus since everyone has different priority.

So "a separate small, experimental product" is not going to work unless 1. the model becomes fully productionized, generally available inside the company so a single VP (or even director) can quickly build a prototype to demonstrate or 2. someone successfully proposes a convincing path to the major billion user product to draw senior executive's attention or 3. the research team decides to build their own product team from scratch and aggressively invest into the sub team.