This is the thing that made me switch to it from Chrome. Something as experience-breaking as refreshing the page isn't something that the user should encounter just through energetic scrolling.
That being said, I agree with you and really like that FF doesn't have a motion for refresh. It's mildly annoying sometimes, but usually it's only on sites very clearly constructed around the mechanism which have no other way of refreshing the page without going somewhere else first. HN is convenient enough on mobile with FF because you can just tap on the HN Title to refresh the page. Other pages are not as kind.
Firefox, Pale Moon, and Chrome all have a refresh command in the "3 dots" menu. I usually use that.
I'm a quite energetic swiper and, to be honest, I have never found a situation where I wanted to return to the top and ended up refreshing due to too much swiping. But YMMV, I guess.
"on sites very clearly constructed around the mechanism"
Browsers have refresh buttons for that.
At this point if Chrome implemented the "open tab in background" feature (when I click on a link in an e-mail I don't want to switch directly to the browser) I would probably switch back.
I use FF Mobile because I want competition and I do like the features Firefox offers, but the performance and UX on Android are definitely lacking relative to Chrome.
Focus is meant for average users, who don't necessarily understand what Private Browsing does.
Having it as an Android Webview wrapper is nice, because it makes the APK really small. This way, users don't have to have two full browser APKs installed.
And well, it's not like it sways webpage owners one way or the other much, to have users use Firefox when they have all trackers and as a result essentially also all ads blocked. They don't make revenue off of those users, so why should they worry about making their webpage work for those users?
On my phone, scrolling by swiping is slow, it scrolls such a short distance. Meaning going down a long NH page takes many swipes. All other Android browsers seem to get it right. Fonts also seem "off".
It's these small things that make the experience frustrating.
I truly want to use it, but it seems the designers of the app don't use other browsers, or have no interest in making the switch and Android FF easier.