Quite frankly I don’t know, hopefully someone else can chime in with more info? If I had to guess maybe something to do with security, but idk with certainty
edit after a quick search, from somone who claimed to be a dev in the comments here: “Apps don’t need to be open-source, split APKs are fully supported, metadata verification is more robust, (unattended) unprivileged updates are supported in the official client, and (in my opinion - you may read the docs for yourself) Accrescent has more strict quality control requirements.”
Saddle bag