To expand on what the "no cheat detection" means and why you can still get banned in group events:
The mod itself is not detectable, meaning that if you installed the mod on its own but never use any of the features, then you could not be banned. JC currently do not have a method of automatically detecting if you are using this mod (as far as I know, otherwise we would all be banned already!).
The problem with group events (full marks and house pride) is that if anyone is reported, all people in the group are checked. JC will check the historical actions of the account and in most cases will see a discrepancy caused by using the mod (numbers not adding up, progress further than it should be for how long you have been playing, abnormally high resources/energy etc...). This means that even if you use a legit client after previously using a modded apk, they can still see the history of the account and will ban you regardless.