Grease Pencil 3.0 fill tool lasso draw has opacity

beacuse the high inacuracy of GP fill tool yo have to often go back in with the lass fill draw. Usual hotkey: with fill tool selected and a solid fill as material, draw pressing shift.

I noticed that in GP 3.0 there are different outcomes depending if you us a mouse or a graphic tablet (tested 2 diefferent tablets and computers)

for some strange reason the ones drawn on a tablett have opacity variety.