I am still on my journey getting around bead production & history. So please bear with me.

I retrieved these 2 pictures from Tasart which show several types of a speo, at least I thought. With chevron layers inside, with drawn stripes, without stripes....
So I thought the moment there is at least one inner layer drawn, sorry which in reality are 3, like the blue/white bead below it can be considered an 'a speo'. In this way a Nueva Cádiz is an a speo and the chevron a special a speo?????

So the not finished a speo aspect of Matt's bead, does it have to do with the vertical lines, which here were not obtained from drawn cane but added through lampwork ? Yet there is a drawn inner layer-- (sorry 3 ). Is it then 'a dilettante' a speo ;-)? I am completely confused now. Is there a strict definition of an a speo? All help is welcome :-)