This was on purpose - they connected it to the internet via a USB-C cable it appears, for consistent internet instead of having it switch WiFi

Probably some kinks there they are working out

> Probably some kinks there they are working out

Or just a good idea for a live demo on a congested network/environment with a lot of media present, at least one live video stream (the one we're watching the recording of), etc.

At least that's how I understood it, not that they had a problem with it (consistently or under regular conditions, or specific to their app).

That's very common practice for live demos. To avoid situations like this:

https://www.youtube.com/watch?v=6lqfRx61BUg

And eliminate the change of some prankster affecting the demo by attacking the wifi.

They mention at the beginning of the video that they are using hardwired internet for reliability reasons.

You would want to make sure that it is always going over WiFi for the demo and doesn't start using the cellular network for a random reason.

You can turn off mobile data. They probably just wanted wired internet.