Warmode Question

While in warmode on alot of my alts, I’ve noticed at war crate that a raid group shows up to battle for it as horde would ( if present) only they’re fellow alliance in RED.
Is that a shard or something I’m missing where alliance vs alliance are hostile now?
A person in general chat even annouces for us not to kill eachother because we’re all alliance.
How does this make sense?

Each zone has a free for all world pvp area and you’re still flagged to others of your faction for a bit after leaving the area