Yeah, seems like LG TVs also do that, just like Samsungs. Again, it has nothing to do with HDMI-CEC, it's just something the TV decides to do by itself when it detects input. My TV does not have this "feature", it only switches inputs when it explicitly gets an HDMI-CEC signal telling it too. Devices that don't support CEC cannot auto-switch inputs on my TV. On yours I bet they can. So, the Switch does NOT send a "switch input" control signal in these cases, but it does seem to send some sort of (video?) signal, and that's what's causing this issue with some TVs. Unfortunately it seems like these TV makers don't allow you to turn this "feature" off.
I believe only the Home button should wake it up from sleep mode. That's what it says before you put it to sleep at least. But I'm not 100% sure it's actually true.