I won't say you're the only one, but generally speaking belt squeal comes from the belt being too loose, either from wear (stretching) or the tensioner spring aging and not applying enough pressure. Sometimes it is caused by a sticky pulley but with yours both being relatively new that shouldn't be your issue. It could also be a glazing of the rubber but again, your trucks are relatively new so I wouldn't think that would be it.
How you drive and how the vehicle is used has a major effect on how long the belt lasts as well. A belt that spends a lot of time at steady state (i.e. long highway drives with very little speed fluctuation) will last a LOT longer than a belt that sees a lot of stop-and-go or a lot of engine on/engine off cycles.
There is also the possibility of pulley misalignment, but that is usually caused by damage or improper assembly - again, this shouldn't be your issue if your trucks have never been wrecked or the engines worked on.
I bought my 2017 brand new and I think I put a new belt on at 60k miles but I can't remember. I'll have to go through my records to check. I'm at 85k now and no belt squeal.
