For years fuel fills have been designed with vapor recovery systems and with what are called vapor space by the SAE at the top of the fuel tank. Topping off tends to drive fuel into the vapor recovery system and can result in damage that can get expensive. The automatic shutoff point of the fuel nozzle is dictated by the engineers and the standards bodies (NIST and SAE).
A diagram of the fuel system is available in the parts listing (formerly called the PET) at
https://assets-v2.porsche.com/us/-/media/Project/PCOM/SharedSite/PorscheClassic/Original-Parts-Catalogue/PDF-EN-US/KAT520_USA_986_04_KATALOG under Main Group 2 fuel system
Your carbon canister may be damaged by repeated overfilling.