It’s hard to know for sure without listening to it but it may very well be as stuttering is quite common in children (usually starting at the ages of 2-4) and most (90% IIRC) out grow it. My advice would be to ignore it and don’t let the kid know it’s there and if it gets worse or persists to seek speech therapy early. Source: I’m a doctor (not in speech though), went to many speech therapists as a kid and still do (still stutter in my 30s) and had a younger brother that outgrew his stutter at the age of 11. My numbers maybe a bit skewed as they’re from memory. But again, always take what is said on Reddit with a grain of salt, including my comment. Hope he outgrows it.