App Store Connect: why "App Promo Codes" is shown for freemium app?

I have recently released a new app, which is free to download and has a subscription to unlock a feature. When I go to "Promo Codes" page in App Store Connect, I find both "App Promo Codes" and "In-App Purchase Promo Codes" are list. I wonder what's the use of the former? This is a freemium app, so I think it's useless?

App Store Connect: why "App Promo Codes" is shown for freemium app?
 
 
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