Is item rarity useless for currency?

The stat "Increase rarity of items found" distinguishes items (Grey, Blue, Yellow, and unique) And says Currency doesn't have a rarity level, only individual rarity drop chance. My question is if "Increase rarity of items found" only affects the likelihood of improving an items rarity from one colour to another, and is completely irrelevant for currency because it doesn't boost drop chance?

In the interviews Jonathan mentioned several times that IR affects currency in PoE2. You should get higher/rarer tier currency more often.