GDPR specifies otherwise than your interpretation, logical as yours may be from a technical standpoint. The site operator chose an optional way to embed fonts

GDPR specifies otherwise than your interpretation, logical as yours may be from a technical standpoint. The site operator chose an optional way to embed fonts in a way that divulges PII to a non-GDPR destination. As there is no legal or technical requirement to embed Google Fonts, the site operator is therefore liable. If use of Google Fonts was mandatory for the web to function, then the site operator would not have been found liable. It is not: they can be mirrored locally, or simply not used, and the web as viewed from the user’s perspective will continue to function just fine. (IANYL, etc.)