Potion ingredients aren't their actual names.

[Rolando]

this is quite in line in how a guild would keep secrets in the oppen.

A guild code book of ingredients would be very valuable.

Maybe the gargoyle gallbladders are used for something else, like containers for some of the concoctions or because you can produce an acid or liqueur with them and this can speed some process, but the actual potion don't need them. Same with some of the other grotesque products they regularly buy.