"f" ascender blurry at ~20 ppem in hinted TTF's

[ortoslon]

The ascender of "f" in hinted TTF's renders blurrier than in several other hinted sans-serif fonts at around 20–24 ppem.

Hinted Inter v3.015;git-7f5c04026 in Chrome 88 on Win10:
For comparison, left to right: Inter Regular 21 ppem, Inter Medium 20 ppem, Recursive Sans Linear Static Regular 20 ppem, Plex Sans Text 21 ppem, Work Sans Medium 21 ppem:

[rsms]

Inter is autohinted (and overwrites any manual hinting programs afaik) so I don't think I've got a way to address this except tune parameters of autohint which means inspecting all other glyphs which is a ton of work. Any ideas how this can be improved?