“It consisted of only 10,239 lines of code.”
Linux v0.01 was 8,670 lines without comments. Today’s kernel is 36 million. The first version hardcoded i386 assembly into include/string.h with no #ifdef in sight, which is exactly what Tanenbaum complained about. The scheduler picks the task with the biggest counter and halves the rest. Portability came later. Shipping came first.