Thanks for your observation! The greyscale values were designed to meet the needs of UI designers for both light and dark modes, with a tighter grouping at the lighter end (from 25 to 200). However, as you move towards the darker values, they become more spread out. So while there is some clustering in the lighter shades, it’s not as pronounced at the dark end. The sigmoid pattern you noticed seems to be purely coincidental, but it's interesting how such patterns can emerge!
Thanks for the feedback. In the future I'll update it to allow you choose your own number of color weights.
In my systems, I often use 12 stops for neutral colors and 6 for all other colors.
Why 12? Dark mode! It's hard to depict elevation in Dark mode with shadows, so we use color instead. For that, you need stops 700, 800, 900 & 950 for various levels of elevation. I then added stops 025 and 050 so i can repeat the same in light mode.
In the past, I have gotten away with using only 10 for neutral & 4 for vibrant colors respectively in the past.