hmmm... I got two updates a few hours apart the same day I got the phone (The first in the store and the second after I got home). After the forced startup the next day, I got one more. (I used the phrase "a bunch" to indicate "several".) I have both "beta updates" and automatic updates enabled. My iPhone now claims to be running 18.1 and is "fully up to date". I have not received the 18.1.1 or 18.2 update yet. Is there a way to expose the version history of the phone?
I suspect that Apple's update process knows the exact configuration of the chipset inside my phone and flows a correct update accordingly. Not all phones are from the same production lot. There may be relevant variations that the update process needs to consider. I also do not know the timing algorithm for updates.
Updating a billion phones across the planet is a complex task and there is more than one way to do it, e.g., the DevOps daily method of near continuous micro updates WebEx uses is the other extreme.