Mostly from personal experience, also saw a few similar cases on Reddit. The banned app had a link to the app's website which, in turn, had a link to xda forum where the very same apk was hosted. Here is the rule quoted in the suspension email:

"Apps or third party code (e.g., SDKs) that download executable code, such as dex files or native code, from a source other than Google Play."

If someone thinks it's an overreach, read about cases when apps were banned due to a link to another Google Play app from the same developer [1]

[1] https://www.reddit.com/r/androiddev/comments/atsju7/linking_...