The explanation about the superior taste of kanthal vs steel and NiCr as follows.
The Kanthal alloy contains some aluminium. When heated up, the kanthal wire, by action of heat and oxygen in the air, forms a tiny layer of aluminium oxide on the surface.
This oxyde is extremely tough, and an electrical insulator.
The hard anodising finish of expensive devices is aluminium oxyde. Sapphire, the gemstone, is aluminium oxyde.
The e-liquid in contact with kanthal finds a better interface, as it is not exposed to the electrical voltage present across the coil, and is prevented any parasitic chemical reaction with the hot metal.
Note that some e-liquids tastes very different, some much less so, depending on their composition.
Hope this helps,