Group stage is BO1 double elimination bracket, I can't say it's worse or better than gxr India, but personally I prefer round robin tbh
I wonder why they didn't use the round robin format, maybe it's because of runtime cost and scheduling? GSL will have 4 bo1s each group, whereas round robin will have 6 bo1s in each group. so you need to have 8 bo1s (two bo1s times 4 groups) extra, that will take at least an extra day or two to run the group stage, maybe that's why they use GSL, but yeah idk, not that big of a deal tbh.
GSL is four teams double elim that they use btw if you don't know