If anyone watches sports, Admirals and Yonkos are like S or A level players, and Yonko Commanders are like role players, or B level.
So if you have
S - Superstar
A - All Star
B - Role Player
In the NBA, "S" would be like a Kevin Durant. "A" would be like a Curry, Klay Thompson, and "B" would be like a Draymond Green.
Role players usually have 1-2 stats that are Top Tier. Jozu might have durability or physical strength that's Top Tier. Marco might have endurance. But they are not well rounded enough overall to be S or A levels.