I sadly can't deem this evidence enough for punishment.
The reasoning behind this is because of these 3 reasons.
1. He could have been manually clicking.
2. The permanent sneaking bug still exists, causing you to see him sneaking while he is actually not.
3. I've experienced particle bugs myself as well rarely, so it's unlikely but not impossible.
4. His skin has his head facing backwards so he's actually looking forward there.
Considering all of this, it is a very unlikely scenario but not impossible so I am giving him the benefit of the doubt this time.
If we spot him doing this again we will be addressing it.