The question is great...
A common complaint for years was that the receiver 'MUST' be on for anything to work.
The wife (or kids) come home and just want to watch cable tv, or play a game. So, they have to turn the TV on, turn on the receiver, put everything on the right input, etc.
Kind of cumbersome. Especially for casual viewing.
So, newer A/V receivers often feature video pass through when off. The receiver typically has several modes and options for video pass through when off.
1. Disabled (doesn't work at all)
2. Use last input. If you leave it on HDMI 3, then that's what passes through. If you leave it on HDMI 1, then that's what passes through.
3. Use a specific input (select input) - Always uses the input that you specify. So, if HDMI 1 was the choice, it would always pass the gaming system to the TV when the receiver is off.
It's a really nice feature for casual usage and not on every A/V receiver, but clearly yours supports it.
You can dig through the setup of your receiver to see what your options are.