Did Home Assistant give devices access to my main network?

Nest Wifi Pro. I had a guest network set up and some wifi devices connected to it.

I connected a Home Assistant OS box with a wire, which puts it on the main network, rather than guest. In the app which controls the Nest Wifi, I selected to allow the Home Assistant OS box to access devices on the guest network. Doing so, in theory, would prevent the IoT devices on the guest network from hitting other devices on the main network.

After adding some IoT devices into Home Assistant, I popped open the Nest Wifi app and saw that they were appearing as being on the main network. Things like light bulbs are listed as having wired connections.

Is Home Assistant rolling out a red carpet that gives IoT devices a path back to talk to any other devices on my main network which they might please? Is the Nest Wifi Pro just stupid? Is something else going on?