I see no mistake or contradiction. Venetian lampwork beads were made one at a time on a core of copper wire. The finishing process dissolved the wire leaving no residual. Finished beads had a polished look of consistent color.
Similar beads were made several at a time on steel rods. The agent used to release the beads from the rods, left a residual that lined the holes with a white color not found on Venetian lampwork beads due to method of production. This may be what Belle had in mind.
"Cornaline d'Aleppo" refers to a type of Venetian bead layered in specific colors. White may be at the core - the inner layer, but it's a specific color of glass rather than a residual color.
"Fiorato" meaning flowered, is another type. We know them as Wedding Cake Beads, typically decorated with aventurine glass in overlaid and trailing patterns. The flowers include rose buds and forget-me-nots. A white color lining the thread holes would indicate they are not Venetian.
Sorry, I'm not expert enough to comment on OP's photo of beautiful beads.
