Blade Arc skill - dont understand

Hi, sorry for my english.

About Blade Arc.

Why is 2h-weapon attack FASTER than 1h-weapon with blade arc?

I read BA its skill so use c.spd etc but when i have the same items, only change weapons from 2h to 1h the hits are slower.

I mean in 10 sec with 2h weapon i hit 22 times but with 1h i hit 18 times.

Why diffrent tempo?

Build arc blade+shield+all sold super shield skills would be amazing but right now…