I think that tool is great for judging the power required for different wavelengths to look similar in brightness but not for judging how much brighter one looks compared to another.
It can say you need 1.4W of 445nm to see the beam as well as 100mW of 532nm but a beam of 2.8W of 445nm is not twice as bright as a beam of 100mW of 532nm.
It can say you need 1.4W of 445nm to see the beam as well as 100mW of 532nm but a beam of 2.8W of 445nm is not twice as bright as a beam of 100mW of 532nm.