Ok
No clue on that, maybe as bill was generated later this month after 20th Dec hence it didn't count.
I'm sure about 18th Dec transaction, which didn't catch any cb for my friend. CC clearly stated as it was settled later and statement generation time is used to calculate the cb and till then already new rules were in place hence it didn't fetched.
They haven't given any info on will monthly bill be eligible for this in future