I did a search for threads containing the terms 'creative' and 'advanced' in this subforum and found no threads describing this bug.
When starting an advanced start game in the ancient age, capital cities and secondary cities bought by creative leaders recieve a free 30 culture at marathon speed. Capital cities and secondary cities bought by non creative leaders recieve no free culture.
Presumably the free culture at normal speed is 10. I don't know if this bug extends to advanced start games beginning in later eras.
When starting an advanced start game in the ancient age, capital cities and secondary cities bought by creative leaders recieve a free 30 culture at marathon speed. Capital cities and secondary cities bought by non creative leaders recieve no free culture.
Presumably the free culture at normal speed is 10. I don't know if this bug extends to advanced start games beginning in later eras.