The following comes with a disclaimer, I've not looked into this in a while.
The answer isn't as straightforward as you may think. Simple answer, that is indeed the case. It will likely work but your friend will be limited to watching a previous recording whilst recording something new.
The complication is that
I think it is possible to record from another channel at the same time if it is on the same satellite transponder. The likelihood is that it won't be on the same place, so mostly it would be the way you already described.
I'm only bringing up what I'm about to because of the way you worded it in the first paragraph. As far as I recall the Non-Recording box of the new 4K FreeSat models has two tuners despite it not having a recording feature, so please be careful.