>>51462660A. To resist Sucker Punch if you’re facing a Bisharp
B. To have it resist Knock Off and the Stealth Rock after getting its boots removed
C. Because of the potential for its checks using Terastallization, especially Pokemon with abilities like having Flash Fire Steel types or becoming Dark type.
D. Because Ceruledge isn’t particularly ideal as a Terastallizer because it’s a frail duel type Pokemon. If you’re gonna lose 2 STABs, you should only do it when you really need to (like Sucker Punch, Knock Off, checks changing types, ect) and Fighting or Dark do that well
Also, we don’t know both their movepools yet besides their signature moves. So for all we know Ceruledge’s Fire/Ghost STABs have lower BP than Sacred Sword or Close Combat (if it gets those, and same with Armarouge too)