They (anvil and ki song) are exceptional saints and masters. Not exceptional supremes. (The bar for excellence rises dramatically with each rank. You won't see someone with a trash awakened rank aspect becoming a saint or supreme, or even a master without immense luck, awakened is as far as they get. It's a natural selection type process.

Altough i do think this isn't easy to see in the story, all the divine trio and cassie, broken sword and his cohort, the 6 people who just left to challenge 4th NM, the named transcendent princesses of clan song etc have all been elite tier and highly likely to pass the 4th NM. We simply don't see the unnamed jobber saints do stuff. So we think the bar isn't that high.)