Gen III Engine failures

Yesterday I had my 2021 at the dealer for a 20K checkup.

Speaking with the service rep and he mentioned they have replaced a number of 3.5L motors, from 2016 to 2019. Mileage varies, the lowest was 30K.

He did not get into the details other than eluding it was piston to cylinder clearance/wear.
What exactly that means I dont know, he further went on to state that Kendall believes it is due to cold starts. (Fairbanks Alaska)

Apparently at some point Toyota no longer offered/warrantied block heaters and the winterization consisted of primarily oil pan heaters.

When I bought my truck I asked about winterization and had them install a block heater at a additional cost.

Any one on here have any knowledge/experience with 3.5 engine failures?