Ok, so this has been going on for months now. I finally got 50% last time. This time I go 0 for 3. This is not random. Something is wrong in the game, and I refuse to spend another dime in the game until it's fixed.
I am sorry you are feeling that the feature is not working, CM said that it is running as it should.
As a player, I can give you my personal experience. There were a couple of times that I got 4/4 oranges... delightful. and sometimes... well, zero oranges from 4 or 5. I only open them just in 50% event or when guaranteed guardian event is running.
Today I got 5 oranges from 12 holy bonds applied. But from those 5, 3 were the guardians I have been waiting for a long time, so that was awesome for me. I prefer lees guardians that I can use than more orange that I will put down eventually. I got a pair of purples I can use too.
CM told us it's a matter of luck. Well, we cant apply maths to luck, I guess. But the moderation team did highlight the complaint about the holy bond drop rate during this event. The answer you already know: it's a matter of luck.
I wish you the best of lucks for the next event. If you were not lucky this time, I'm positive you will be next time! Let us know!