I didn't run into an event bonus stage yet either but I'm hoping it's just bad luck.
Also, with her new version Cepha has joined a small group of Knights who jumped at least two stars of rarity between original and new versions (going off of memory mostly so I'm probably forgetting someone):
- Cyclamenn went from 2* to 5* (Radiant Princess) and 2* to 6* (Seven Flowers) - probably the only instance there will be of a four star jump
- Mint went from 2* to 5* (Maturing Virtue)
- Alstroemeria went from 3* to 6* (Anniversary/Gratitude Towards the Future)
- Nymphaea/Egyptian Water Lily went from 3* to 5* (Maturing Conspirator)