These things have existed fo awhile now, I've seen an Anker one on Amazon :/ What is so special about a power bank with a ring of magnets? If anything it's worse for the environment lol.
I guess it's something about just popping it on without a case or any kind of straps or anything that's supposed to make it appealling in a sort of futuristic, 100% wireless and minimalist way.
The thing is just, as many YouTubers have pointed out, that the magnets on most of these packs, both third party and from Apple, only work well enough when pushing and pulling in certain directions and almost not at all not in others, resulting in it quite easily coming off once friction is applied.
So in the end, it might be much easier to use these MagSafe battery packs than, say, having to slip on something like the Apple Smart Battery Case, and the footprint might be also be smaller for a lot of them(not sure).
But they don't hold on well enough for you to slip the whole iPhone + battery pack combo in your jean pockets, or really any kind of pocket or bag where something might push or pull on the battery pack.
Considering how less-than-optimally they stick to your iPhone and how a lot of the mAhs will be lost to heat and never charge your iPhone's battery, then I don't see how valuable these battery packs can be unless they're dirt cheap.
Sure, it looks a lot sleeker and probably is better integrated into iOS than most other options. But I would care less about how it looks if it's just there to get my phone through a very long day... which I'm not entirely confident this can do for me.
Since Apple isn't mentioning the "up tp 50% longer battery life" claim that they did for the Smart Battery Case for the iPhone 11, then I'm thinking this would only add something like 25-40% longer battery life.
The MagSafe Battery Pack is big on features but low on mAhs.