Envenomed bullet clarification

The skill description for the basic Engineer skill “Envenomed Bullet” reads as follows:

You can use a Venom vial on a Bullet before loading it into a gun. This expends both the Bullet and the Venom vial, and the next shot from that gun should use the call “Venom Pierce”.

When it says it “expends” the Bullet, does that mean using this skill also expends a use of the True skill Bullet? Or must it be used on the engineered item “Bullet,” which refreshes one use of the Bullet skill? Or does it simply mean that physrep should now be considered covered in venom until it is shot from the gun?

Nontrue engineers get Envenomed Bullet, but don’t have the regular Bullet skill though. I’ve never seen one skill require another skill to use anywhere else in the rules so I assume that’s not the intent.
I had assumed that it meant you couldn’t use it to fire two darts consecutively, because the first is still considered a bullet the way that Tranq dart and Glue gun are?

A related question, though. If the physrep bullet (nerf dart) is considered covered in venom does that mean touching it would have the same effect as a blade doused in venom or contact poison? Assuming you dont fire Envenomed bullet for whatever reason, what then?

1 Venom Vial + 1 Bullet Skill + 1 minute of loading time = gun loaded with Venom Pierce

The engineered item “bullet” is a refresh of the Bullet skill.