I can't read French, so I didn't access the site. However, we have (to the best of my knowledge) always had party hunting in Ontario, and I'm a staunch supporter of it.
It is particularly valuable when a group relocates to a remote location to hunt, and the chances of success are relatively low. In these circustances, if a member of the group is successful on (say) opening morning, he would otherwise be prohibited from hunting for the remainder of the vacation, and forced to remain in camp and - what - drink.

Meanwhile he'd have to wait 'till evening and listen to his buddies talk about their daily adventures.
To me, party hunting says to the general public that this (hunting) is a legitimate recreational activity, and the time afield is the thing of the greatest value, not only the meat or trophy from the kill.
When game populations get to a point where success is almost a given, a group may decide within itself to limit the kill, so everyone can share in the success, but (to me) that should be a decision of the group and not the law.
In observing my own hunting camp (deer) over the past 45 years, our over-all success rate is around 50%, and there is a hunter with a second kill about once every 9 man/seasons. So a party of 10 guys would (theoretically) get 5 deer, and one of the successful hunters would have 2 kills. This would leave 5 tags unfilled. We designate tag usage on the basis that those hunters who would be finished hunting after the current hunt use their tags first, while those who hope to hunt elsewhere in a later season use their tags last, and are likely to be able to preserve them.
It me an additional (or party) tag is an additional opportunity to hunt, not a licence to stock up my freezer. As I've said many times before, I hunt because I love to hunt, and any meat or trophy I come home with is merely a bonus.