Right, remember that Tesla measures all it's "performance" version with rolling start. So your M3P is 3.1sec with rolling start. The X is 3.5sec with rolling start.
M3P: 0-60 3.1 (rollout subtracted), 11.6@115mph
MX: 0-60 3.5 (rollout subtracted), 11.3@123mph
Your can see what is happening...