205.2a: The card types are artifact, battle, conspiracy, creature, dungeon, enchantment, instant, land, phenomenon, plane, planeswalker, scheme, sorcery, tribal, and vanguard. See section 3, "Card Types."
It looks like they forgot to update one of the rules, but remembered the other. Regardless, the card rules text always takes precedence over the comprehensive rules (not the reminder text though, anything in italics is not rules text), and rules have been created for how battles work, so they should function as usual I'd imagine.
Some cards ask for a card "of a type not already chosen" or similar, so if Battle isn't a card type, it wouldn't be a valid target.
Others might ask for a nonartifact, nonland etc card, and Battles would be valid, as they should.
Worth noting as well, but even if you ignored the "Battle" type on the permanent, it is already possible and well within the bounds of the rules to have a permanent with no types (for example, mutate on top of a Theros god and lose the required devotion).
your link returns not found for me
That's odd. Tested it on multiple machines and it works for me. Regional issue? can you find it on https://magic.wizards.com/en/rules?
It works for me, maybe regional then.
It just auto downloads a PDF fille, check your downloads
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