"only XL-2"

Bottom line: according to the judges, it's better to immediately report any issues to them. It's like in kindergarten, whoever complains first is considered innocent.

Look at the situation from the perspective of a host – there's a task to give technical support to someone, but to whom?

I act in the same way – if one player is writing and the other isn't, then technical support is provided to the first player in case of a lack of results. It's often too much effort to run around and ask "how's the game going?", but it's usually not difficult to respond to player emails.