A Description of <mask> may be wrong

[zhangzhuang15]

Visit https://developer.mozilla.org/en-US/docs/Web/SVG/Element/mask, the first sentence is "The element defines an alpha mask for compositing the current object into the background. "

I don't agree with this point.<mask> seems to define a luminance alpha by default, and developer can change this by setting mask-type alpha. In luminance mask mode, there's no difference if your path element follows fill="white" or fill="black".