Thanks for the replies. truly appreciate them.
He is actually going home to Manila in January 2023 to formally ask the parents' blessing for marriage. They have known each other for years, and it's kind of like an expectation for both families that they will, after graduating and having stable jobs.
Q: If they decide to get married in January 2023 ( I do not know yet if they will, I am just speculating, since they have long waited for this), how do we proceed? Do we just inform USCIS that we are changing the K1 to CR1?