They _did_ serve the data. From TFA:

> To demonstrate its scale, we operated the instance with 100M bots posting 3,500 times per second at 403 average fanout.

The linked post about their demo [1] has more details about the challenges involved, including rendering home timelines.

[1]: https://blog.redplanetlabs.com/2023/08/15/how-we-reduced-the...

Meh,its better than nothing, but real world traffic is often very different than simulated traffic. If it isn't actually working with real traffic than i am not impressed.