Coordinated Assault

The reason this reads as a combat trick and not just a pump spell is the second target. One mana that touches two creatures at once is doing the math of a blowout: in a stalled board, attacking into open mana, the defender reads a single trick and trades accordingly, then watches both blockers die before they connect because both attackers struck first. First strike on two bodies simultaneously is the part that rewrites the combat step, and the +1/+0 is mostly there to push a creature out of trade range against whatever it now strikes before. It is a go-wide aggressor's tool by design, not a one-on-one duel card: the value scales with how many creatures you have on the table and how many blocks the opponent has committed to. That reach comes at a price, though, since the card does nothing alone and asks you to have already built the board it wants to protect, the trade red aggressive decks have always been willing to make. It sits in the lineage of cheap instant-speed combat manipulation where the trick is not the buff but the timing window: you hold up one mana, the opponent has to respect a double-pump-plus-first-strike line on every attack, and the card does work whether or not you ever cast it.