Capulettium Plus does not prevent movement.

[Cirrial]

So, capulettium plus still allows vision and prevents the victim from speaking or emoting, but using items and moving around is still absolutely fine.

I'm not sure if that's intended?

[Mordent]

Doesn't look like a bug to me. From the wiki:

Instant and ongoing vocal paralysis until chemical fully depletes, also prevents the use of all emotes. Makes the victim appear dead if they're laying down or sleeping.

This essentially lets you play possum. You're unable to speak (excluding telepathy or machine talk), but you can make yourself appear dead in a pinch. Know someone is hunting you? Inject yourself with this just before they find you, lay down and they'll mistake you for a corpse! You retain full consciousness and control of your body, so you can back up and ambush them when they least suspect it.

[UrsulaMejor]

Cap+ lets you play dead by lying down on the ground, if I recall correctly. It's meant to be a more beneficial version of capulettium. This is probably intended?