The /locate command always returns a z-value of 64 (or 32 in the case of /locate Stronghold), though the x-coordinate is correct.

Example: My game has located an ocean monument at x=-1364, z=64, (world seed is 33). Teleporting to these coordinates finds me in a savanna, where there is certainly no ocean monument in sight. According to Amidst, there is indeed an ocean monument along x=-1364, but the z-coordinate is -1176. This is not particularly close to the provided value.