I had an early RFIE too, 10 days after NOA1, but it was for the I-864 (we had forgotten to send tax documents). I’m not sure if having an early RFIE is an indicator for fast processing. Instead, we might have received an early RFIE because our field offices process AOS quicker. It also seems to me that most of K1 AOS filers get processed quicker these days, compared to people adjusting from F1, J1 etc.
My I-485 still says “approved.” I just received in the mail my updated SSN card with my married surname. I thought I had to go to SSA on my own to update my name once I receive GC on hand. Glad that I won’t have to do that anymore. Prolly because I had checked “yes” for question 16 “do you want the SSA to issue you a social security card?”