Can confirm as per English description Intervene should Stun (2s) but currently is not stunning.
It was one part of the Paladin's kit I was excited for, 3 Stuns (1-Shield Bash, 2-Intervene).

But what's worrying is the Japanese Intervene PvP description has no mention of:

"Addition Effect: Stun, Duration: 2s"

Hope Paladin were meant to have the Stun additional effect on Intervene as per English description.