So if I understand that correctly, then the TypeScript compiler source consists of ca. 250.000 lines of code (LoC). According to the video, the scanner has ca. 2.600 LoC (~1%) and the parser has ca. 9.000 LoC (less than 4%), so in total scanner and parser together need ca. 5% of the entire codebase… Ok.
Yet over the years I have collected ca. 30 books about compilers and a lot of them talk way more about scanners and parsers (up to 70%). You go figure…