Glove fingering

I've noticed a peculiar habit with some young players. My son, an 11 year old, holds his catchers mitt such that he avoids the index finger altogether (jamming an extra finger into the big pinkie slot so that his index finger ends up one over). He says it gives him a bigger (almost softball-like) pocket. I tried it and he's right! I also notice that the Wilson kids' glove specially designed with a huge pocket, only goes with three fingers anyway, creating the same sort of cheat that my son is doing himself. It does off-centre his pocket slightly (alhtough I don't see any problem with the slight shift in the centre). It also keeps his hand seemingly hanging out the glove a little more that a full five-fingered glove hold, but that didn't seem too problematic either. Yet I don't seem to see any serious players or pros hold their gloves in this manner. What is wrong with this type of hold? Is it good? Good just for kids? Anyone else have any experience with this technique? Thank you all. Regards.
Jeff from Canada.