Is he riding with others, or is he likely to join friends or a club doing those types of rides? If so, then it will probably be best if he gets a bike similar to the others in the group.
You can tour and ride light off road on almost any bike, but if you are riding with others it’s best not to be significantly ‘overbiked’ or ‘underbiked’ compared with the group.
So if you ride with people who are doing 80 mile day rides on road with a bit a roughstuff on relatively light traditional touring bikes, he may be handicapped (even if very fit) if he rides with them on a MTB. Conversely, if the group ride MTBs or fairly beefy wide tyred gravel bikes like the Genesis Vagabond, a lightweight tourer may not be up to the task for the off road bits the group is likely to choose.
If you ride solo, then you can ride whatever you like, including bikes that others might consider unsuitable: if you are happy and enjoying yourself nothing else matters, including whether or not others think you are riding the right bike.