Y'know, I intentionally didn't use the term "sideloading." To me -- and maybe I'm just being silly -- sideloading is when you download an installer file (or an APK on Android) and force it to install outside of a store. Apple's not really letting you do that. Just allowing for alternate stores. Am I being pedantic? Probably.
I actually agree with your decision.
iOS has long supported sideloading on one side, for proprietary entreprise apps that are pushed by an MDM. In a previous life, I have deployed and pushed such apps to iPad devices (when they were still on iOS).
On another side, the apps will still be validated by Apple through a process similar to macOS’s notarization. From an end user perspective, this is quite close to the way the App Store already works, except you’re going to be another storefront.
Voluntarily getting an app still goes through an app you get from an app store, so I will personally call it “installing an app”.