And 13.3.1 beta 1 has a newer kernel (19.3.0 built on December 8) than 13.3 (19.2.0 built on November 4).
I think it's unusual for Apple to use a newer kernel in a small point release. They might want telemetry on the stability and performance of the newer kernel so they released it before the holidays. Just speculating here.
I think it's unusual for Apple to use a newer kernel in a small point release. They might want telemetry on the stability and performance of the newer kernel so they released it before the holidays. Just speculating here.