Not sure whether this is a font feature or a quirky design customization.

Phi  Vorgeschlagen von akira1975 

It’s Phi, a custom typeface, designed by Studio Feed for PHI.
https://www.studiofeed.ca/en/studio/case-studies/this-is-phi

Thank you!

My pleasure!

You might like Youth Grotesque and Cy.
https://feedtype.ca/en/typefaces/youth-grotesque/
https://supertype.de/fonts/cy

..and Fractul:
https://fonts.adobe.com/fonts/fractul-variable