Sorry but that is actually 100% wrong. He doesn't host any IPAs himself/on his server. You DO download the apps from Apple's AppStore or as a backup with the MixRank website. He has said this himself personally if you take a look at some of his recent posts where multiple times he explains exactly that is how it works. The only thing that is "crowd sourced" are build numbers themselves for use with the manual installing of any specific version. If he was hosting every single apps and all its different builds, you would literally need a server-farm of storage available just for IPAs. So again (and please go look at some of his recent posts because he is saying exactly what I have said and will prove you wrong...
I will just leave this link here for you to read and learn were the AppStore apps are actually pulled/downloaded from as well as when you manually install IPAs by using a specific build number, they are pulled from the MixRank IPA database.
One comment says:
-"If you use Appstore++, when you do a manual install, it brings up MIXRANK, but the IPA files are being pulled from the Apple database.
-"It's still being downloaded from Apple's servers. Appstore++ works by modifying parts of the request to send the previous version's id number instead of the most recent. Apple still sees this as valid and allows you to download and install the app."