You’re right. The junction of Osgood Trail with Great Gulf Trail is past the wilderness boundary sign (by six minutes, according to the time stamps of my photos of the signs), but the tentsite itself is outside the wilderness boundary, which follows Osgood Trail exactly, apparently. But the group of young kids on The Bluff would have been well inside the wilderness.
The regulation on the sign by the parking lot states, ‘‘Groups of more than 10 are not permitted in the Great Gulf Wilderness.’’ In smaller type, the next sentence is, ‘‘No more than 10 people may use a campsite at one time.’’ My interpretation is that the first sentence precludes 11 or more persons from hiking together. In the Adirondacks, I believe it is against the regulation for a group exceeding the limit to even start legal-sized groups at different locations or at different times if they plan to meet eventually. In the White Mountains, the regulation seems to prevent a large group from hiking together, even if it subdivides later to camp.
But I could be wrong. And there was no one to report it to, anyway.