local fonts - tests shows source incorrectly?

I’m using local fonts. If I check that local fonts are used (from web browser developer tools) it shows correctly. when I test page from webpagetest, it shows that webpage is loading fonts from google.

why does this happen?

Generally that means you are using a local font that is available on your machine but not the test machines (i.e. it’s not necessarily a web-safe font with a broad install base) with a fallback to the Google font.