Yup, this is all correct!So let me give you a run down on what cannot be dyed via GoryVials.
Metal items.
Pelts.
Foraged items.
Artisan items.
Gems.
Shells.
Generic treasure items (a gem-inset baton)
Even if a scripted item allows dyeing, the above list will still be blocked. Scripted items, by default, deny dyeing though.
I tested it on wood:
>pour my blood on my staff
Pouring the dark coagulated blood on a quarter staff will permanently stain the staff in blood, altering the way it looks. If you REALLY want to go through with that, try pouring again in the next 30 seconds. The end result will look like a quarter staff soiled with dark coagulated blood.
>pour my blood on my staff
You pour the dark coagulated blood on your quarter staff, dousing it with blood.
>glance
You glance down to see a quarter staff soiled with dark coagulated blood in your right hand and a phial of dark coagulated blood in your left hand.
You can also alter the vial to change the description of the dye, so if you made it frothy oozey blood, it would dye things that way instead.