Pro only gives you longer support periods, not extra support during the normal support period. That and livepatch and some other things i forget. But all updates within the normal support timeframe for a given release are the same with or without pro.

My understanding is that everyone gets this at the same time.

Ubuntu Pro provides security updates for packages that wouldn't otherwise be supported by Canonical at a given point in time. If your version of Ubuntu is still within the (non-extended) support period, kernel security updates are always provided regardless of Pro.