Yes - you've got it right. it looks like the Dux Pro and the Dux Pro Plus pencil holders are made from the same protective material. Because they face different ways in the Plus the pencil cozy interferes with the cover but in the Dux Pro any added cover would not come in contact with the pencil holder. It's clear in the pictures on amazon and the STM site.
I put both the pencil cozy and the little charger piece holder on one charge cable so I store the cap there when I'm charging the pencil. The pencil goes in and comes out of the pencil holder smoothly enough that the cap has never come off accidentally.
I put both the pencil cozy and the little charger piece holder on one charge cable so I store the cap there when I'm charging the pencil. The pencil goes in and comes out of the pencil holder smoothly enough that the cap has never come off accidentally.