How does the Monochromacy color space simulation work in Android?

Question

I recently read about desaturation works in GIMP. Since I am a heavy smartphone grey-mode user, I wondered how the colour conversion works in Android.

I did not expect it to be a naïve desaturation as overall it looks very pleasant; I was more expecting LAB Lightness (L*). However, my tests showed that it does not use perceptual lightness – in fact, I could not replicate this effect in GIMP.

I tried searching for this but did not find any results.