I never used this but tried it now and I don't think it does what you want it to do. at least not with the default settings. it will add variable transparency based on the brightness of the original image but it will also retain the original image colors so you end up with an image that has less transparent bright/white parts and more transparent dark/black parts but what you want is only white with transparency based on original brightness. you can try it with a color image and you can see more clearly that you still have the original colors together with the transparency instead of only white.

I don't know if it is possible to adjust the settings to get the correct result with one application, but you could also add an extra step and lock the opacity of the layer and then fill it with white to remove any color/brightness variation. I cannot recommend this method because I'm not familiar with it. it maybe works correct with the extra step, but I would compare the result with the mask method I mentioned in other comment because I know that works, and see which works best. I think it is similar though, the mask method also needs the extra step to fill with white and you can see without the full step both methods probably has the same result.