I'm guessing they scrolled down to the generic MagSafe promo above the product info section and thought the MagSafe wallets (that have been out for a while) were battery packs
Ah, yeah, that's what I did. I haven't had any reason to ditch my 6s so I don't keep up with this stuff too much.
To be fair, it's not a great design choice to shove an ad in between the purchase section and the product/compatibility info