Hey, thanks for the official term.

That headline is only a little bit misleading. X1 support for Linux is basically garbage. So if they're promising X2 support already, I don't believe them because almost none of the devices that have X1 in them are actually fully functional.

I'm assuming that it is similar to the trap in your sink. Except because hydrogen is the lightest element, it has to be upside down. Confident that this is for preventing backflow when the valve is closed and the pipe is opened for maintenance.

Edit: I appear to be incorrect and it has to do with handling the expansion and contraction of the pipe.