There’s a theory that’s been supported by user reports that the 175 Conquest from completing the 4 battlegrounds quest is not counting against the 2500, so if you have completed that quest you’ll actually have to clear 2675 Conq points.
It’s reasonable to report as a bug that you’re not clearing the achievement when you fulfill the stated conditions, but if you want to get the reward without waiting for the devs to fix it, you might try getting the additional points.