Discovering devices in two different subnets

So I am brand spanking new to HA, and have just installed it via Docker Container in my Ubuntu file server. I have a Unifi dream machine and have configured a separate subnet for all my IoT devices. (I have found a few threads similar to this, but I’m experiencing something unique I think).

The network my HA server is on, along with my plex server, roku’s, Harmony Hub, and home pc’s are all on 192.168.1.x. My IoT devices (switches, plugs, Alexa devices, etc) are all on 192.168.2.x.

Upon first startup, HA automatically discovered my Printer, Roku’s, Harmony Hub, Pioneer receiver. Things that are on the same subnet as HA. I tried to add the tp-link integration, and it couldn’t find any devices. So I started looking into how I can discover devices on the other subnet.

I come back about 10 minutes later and there is a notification saying it found a new device. It was one of my tp-link switches. I checked, and it is indeed on my IoT network, 192.168.2.x.

So it seems that it can automatically discover devices on that network. But why is it taking so long? And will it discover the rest of my tp-link devices eventually?

I also just realized that my Chamberlain MyQ garage door is also on the IoT network, and it found it no problem. Thoughts?

Edit: Another tp-link on my IoT network was discovered overnight. The switch for my bedroom ceiling fan lol. How is it deciding what devices to find?