Has there been a change in how weapon quickness affects style damage ?

Different weapon speeds did and still do not affect the extra style damage when the actual swing speed is the same, which would usually be the case if you reach swing cap. If you for example have a 3.5 and a 2.4 weapon and reach swing cap with both you'd see the same style bonus but, due to the different base / unstyled damage, a different total.

Base damage only cares about the weapon dps, weapon speed and the damage modifier which is a representation of everything that goes into weapon skill as well as the enemy armor/absorb/resists etc.

Styles are a fixed bonus based on actual swing speed, style spec and specific style values (which can usually be simplified into a single growth rate) as well as the damage modifier. Some styles are a bit special, for example the stealth opener have a static swing speed.

Since most people are more familiar with growth rates and are viewing styles as multiplier on base damage, we show it as such. However, this kind of breaks down on stealth opener (where we don't show it), the starter styles and styles for LA users as the LA penalty only applies to base damage but not style bonus.