It's not "in fact", "explicitly noted" that Mihawk has greater "Sword Skills". That s on the end matters.
It's specifically "
Swordskill" which in japanese can also be "
Swordsmanship". The line is supposed to be interpreted as "He has greater
Swordsmanship than even Red Hair, he is the
Strongest Swordsman in the World."
Oda literally said that Mihawk is the greater Swordsman with greater Swordsmanship than Shanks and is the "world's strongest
swordsman". He did say that Mihawk is stronger, you just focus too much on the word "skill".