I hate to answer your question with a question, but since this is a mystery, I don't think you can logically consign yourself to one of Richards options. Not that those ideas aren't logical, they just don't quite fit, or satisfy me as a Catholic.
The commentary in the NABRE is not very useful, it just says not to doubt the veracity of the verse.
But here's the question that I'll pose as an answer, what did Jesus hold back from His disciples? Nothing at all. It would seem as though it was God the Father's will for His Son to reveal everything that we need for salvation.
Do we need to know the day or the hour? No
Do we need to be ever vigilant? Yes
So, the more important thing is not that the Son does not know what the Father knows, it is that the Disciples (and us) know what the Son knows.