The group is not losing out because the group member is still paying for the flights as if he was flying.
That's what I was going to say....
I'm sure in our group if a group member is flying with someone else, then the someone else gets to fly our aeroplane. I have no problem with that at all, as long as the time is logged as if it was one of the members, the member is responsible and that none of the members lose time as a result. Makes life more enjoyable - I certainly let my mates fly with me.......
Mind you there are only 4 of us and we're honest. I know that one of the others fighter-pilot mate has showed him how to barrel roll it
(yes it is cleared for it and has a G meter)....