I hit quite low on the bat, so toe it more often than desired. As a result, a very minor version of this has happened to a couple of my bats. It never gets wider than 4cm, (much more of a controlled drive player) so I think ajmw89 is right, perhaps your friend is hitting the ball hard!
I would glue it up and seal it with some shoe-goo. My friend has broken two bats in the last year on the inside edge toe area, I'm planning to stick a toe guard on the face of the bat to prolong the life of his bats!
Slightly off topic, but does anyone find that GMs tend to delaminate quite often? Maybe it's just because the folk at my club use their GMs like crazy, but I find they are at their most responsive when that sound starts coming, and most of them do reach that level.