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does it apply to other butted-to-1,5 spokes as well?
All of them. Torsional stiffness is proportional to the 4th power of diameter, so 1.5mm spokes wind up twice as much as 1.8mm spokes. For axial and radial stiffness of a built wheel, they're fine, they have the same longitudinal stiffness as CX-Ray/Aerolite, but they confer no advantage which is worth having in exchange for being a massive PITA to build.
I'd not use lasers in anything, ever. Wind up way too easy, stiff as wet noodles.