I’m thinking that the jar they provide is a tiny wrapper (28kb) around all the SDKs they inject in the resulting APK, and from what I could tell it seems to be needed for all SDKs:
Interstitial ad:
FGLEnhance.ShowInterstitialAd();
Reward ad (video):
FGLEnhance.ShowRewardedAd(FGLEnhance.Placement.PLACEMENT_NEUTRAL, FGLEnhance.Trigger.TRIGGER_USER_ACTION, OnRewardGranted, OnRewardDeclined, OnRewardUnavailable);
Analytics:
FGLEnhance.LogEvent("event_type");