He won the WBA title against Cotto, and then unified that belt with the WBC belt he won against Canelo.
The Canelo fight was at 152. Floyd's only 154 fight was Cotto. It's splitting hairs, but while it's fair to say he unified 2 junior middleweight titles, he did not unify anything at 154.
While we are splitting hairs, there is no such thing as a 154 or 147 lb. division. They are called the Welterweight and Junior Middle Weight divisions. Of course, you know what is meant when someone says 154 or 147. It's pointless to argue semantics.
This is why he will be considered one of the greatest of all time. 4 lineal champions, 2 right now simultaneously. 147/154. He will possibly beat Garcia for his as well..... 3 at the same time. THEN 160. 4!
I'm actually starting to think historically Mayweather-Cotto II for the lineal MW Title is bigger than Mayweather-Martinez for the same belt. If Cotto beats Martinez he'd arguably be an ATG, he's already a HOFer. Martinez isn't a HOFer in my estimation even though I root for him wayyy harder than Cotto not to mention Cotto is closer to prime than Sergio. I think Mayweather-Martinez is a great fight and would like to see Mayweather vs the winner regardless but again I think historically 2 HOFers/ATG's fighting in a rematch is more significant than just beating an average dominate champ