I didn't want to get into this too much because I'm not a Android vs. iOS debater... if you're not into iPhones and such that's cool.
But the 12 will be their flagship model. The fact you mention your wife and daughter would never buy it for the screen size alone doesn't mean a thing. And if you're the type that think because the available screen size is still smaller than Samsung's and makes it any less of a flagship then that's cool... you're wrong... but that's cool. Because having the biggest screen and the biggest battery doesn't mean it's the best flagship. I mean having the biggest zoom doesn't make the camera the best when it can't take a usable pic at 100x or even beat some of the current best with smaller sensors.
4GB of RAM weak link... that's why I don't like Android vs iOS comparisons like that because you see in tests, the iOS will hold it's own and maybe even excel in tests without needing 8 or 16GB RAM. If specs matter then we can talk processor how benchmarks on the current 11 already outperform the S20 Ultra. Again it doesn't matter because they run two different platforms, but technically, the processor spanks the SD. Some people actually say the iPhone 11 Pro Max, with the smaller battery, has better battery life than the S20 that has a bigger battery. But at the very least it holds it own with battery closer to S20 size.
(Edit add)... And... if you are comparing with an Exynos version, then you're in worst shape in performance and battery.
https://www.techradar.com/news/iphone-12-may-be-twice-as-fast-as-the-samsung-galaxy-s20
I know you said "Except that the base 12 can't come close in specs to a base S20"... but we just don't know until it comes out so didn't say anything.
But "specs" processor-wise... the S20 is already beat with just the 11's processor so your point was moot. The camera?? I won't discount iPhone might not be able to put out a better performing camera when with less camera's than the S20. Again, I don't go wow over big numbers like more cameras or 108mp or 100x "Space Zoom." Google I think shows you could have a banging good camera with just one lens and some people argue it still take better pics than some current phones. The battery life could end up being better than the S20... dunno yet. But too early to see the S20 beats the 12 in all specs.
We'll have to see what Apple ends up giving us and how it performs but I wouldn't go by numbers and think what you're getting from the regular phone is still not flagship phone. You will probably see a lot of S20 vs iPhone 12 reviews and if Apple does it right, you just might see and be surprised of the results. But I will say I am only speaking for myself so if others don't feel the reg iPhone 12 is not a flagship model then thats cool. I guess you don't think the reg S20 is part of Samsung's flagship line but I do.
My point is it's not a flagship phone and it is just branding. Other OEMs have non flagships for the same price or less. It will sell but even non tech people like my wife and daughter would never buy it just for the screen size alone. As far as performing like a champ, the 4GB of RAM is a weak link. Scrolling lots of pages and images causes scrolling to jump back to the beginning. Glad to see they are going to 6GB on the higher end models. The only thing it's got going for it is longevity in support, but how many people even pay attention to updates. Not one person in my extended family or even friends ever worries about updates.