The Switch 2 has a new hardware size and some software (like Labo and Ring Fit) has a physical component that is sized to the original Switch/Joy-Con. It could be referring to that.

I didn’t think any devices even adopted Ethernet over HDMI

That is how it works. Unwanted tracking notifications only trigger if separated from the owner for some time. It’s possible the paired iPhone was drained or had Bluetooth disabled which would cause the tracker to think it’s separated.