I don't expect my mom to need iPhone 12 performance, but even my mom told me her older LG G-something was slow getting slow, and having played with it before her switching phones, it wasn't nearly as choppy looking as this video.
You and I obviously have very different definitions of "quite smoothly". And specs related or not, UI is a major part of the experience. The initial point still stands: Linux phones are pretty damn far from being anywhere viable for anyone but the most hardcore enthusiasts.
> specs related or not, UI is a major part of the experience
When someone buys a phone (or hell, a computer), they're buying a package of hardware, which dictates available software. Hell, you could make some hypothetical $200 phone with the best hardware on the market, if it doesn't have what some people consider "basic" functionality software side, they won't buy... coming back to the initial point that Linux phones are not ready for prime time.
Choppiness of the UI is not caused by the hardware specs, but by not yet fully optimized software. See here: https://social.librem.one/@dos/104984930233748319