Does Spell Perfection allow Quicken Spell to reduce a spell’s casting time?

The Quicken Spell metamagic feat lets you cast certain spells as a swift action (instead of a standard action). This causes the spell’s slot to increase by +4 levels.

The Spell Perfection feat has several benefits, including the following:

Pick one spell which you have the ability to cast. Whenever you cast that spell you may apply any one metamagic feat you have to that spell without affecting its level or casting time, as long as the total modified level of the spell does not use a spell slot above 9th level.

The text says “affecting” the casting time, rather than “increasing”. So how does this interact with Quicken Spell, which normally reduces the casting time?

Can the spell be cast as a swift action (as per Quicken) without the +4 spell slot increase?

Or is the spell’s casting time unchanged, thereby negating the benefits of Quicken Spell?