inconsistent rendering of profile image underglow

here is how https://degrowth.social/@yala's profile looks (they seem to have a profile picture of a single pixel png:

heres what mine looks like which is also a transparent png (I think it looks good)

heres @cheeaun's which has the cool underglow from the header image

and here is one that has barely no underglow https://mastodon.social/@mntmn