Certainly would be, Bros.
I can't imagine any circumstances where it would take three months to decide that enough evidence exists for a D&D charge. As you say, it is usually a "there and then" arrest and even if it was decided to proceed at a later date, I cannot imagine an arrest being made (I'm not even sure that it is an available option after the event).
Furthermore, I imagine our hard-pressed upholders of law and order have better things to do than to arrest drunks three months after they have sobered up!
Perhaps Suzy~Q could provide more details.