It might be an older bike with carbs, if it's cold then he'll have the choke on to start it, then in for a a little while as carbs typically run like crap when cold.
Mine revs at 3k with the choke on fully but even then I'll only have it on full choke for 30 seconds maximum, choke down to half and then ride away.
Modern fuel injection systems will have the revs high for a few seconds after starting, so it's probably an old bike.
Also, what feels like 3-4 minutes is probably 60 seconds, and if it's a big v-twin, maybe an old Ducati then it will be loud no matter the exhaust. And at 6am everything will seem louder.