Literally he wanted to see the "power difference"
"the true distance", exact same thing Zolo said about Mihawk;
You got bodied again, but we know you always run away as you run away many times against me before, so whenever you read a Zolo chapter you think you can argue against me.

Don't waste people's time as I told LA00, you clowns always run away.
That determines who is stronger overall, not stronger swordsman ZKKclown. Alber and Zolo conversation proves this.
Make the rankings then.
Mihawk wasn't even more powerful than Kaido.
WB > Kaido > Mihawk.
Of course there is a big Haki difference between WSM WB and WGS Mihawk.
WGS Mihawk literally being best swordsman but still being canonically weaker than WSM WB mean one thing; Mihawk's Haki wasn't even close to WB that's why WB is WSM over him.
If Mihawk's was close to WB, with WGS difference, WB wouldn't be called WSM over Mihawk since Mihawk would have WGS advantage, but even with WGS advantage, that WGS difference wasn't enough to close to big Haki gap with WSM WB.