Additional thoughts on my take of US Unlocked update scenario.
1. Samsung now doesn't wait for carrier certification just for pushing the security patches. Meaning they can push updates first Monday of every month just like the Pixel does. That's why irrespective of what SIM you have every US unlocked model is getting the security patch at the same time last month and this month.
2. For feature updates, looks like they have to wait for the carrier certification and the ATE6 is only on T-Mobile carrier variant and still not on all carriers. So may be we won't see that on the US unlocked model until all carriers have received the ATE6 update.
3. If point 2 is true, then if US carriers push out in the middle of month then will Samsung wait till next month security patch to push the update on US unlocked model or just push the firmware update middle of month has to be seen.
But overall I'm happy that at least the security patches are coming asap without waiting for useless US carriers.
Obviously this is just my observation based on limited pattern/data set.