I'm sorry, I think I misunderstood your initial response. I thought you meant to say that it is unclear whether people coming in through U4U are allowed to adjust. But now I think you're saying that people coming in through U4U are allowed to adjust, and people adjusting are currently getting Green cards in about a year.
The "ifs" we were concerned about would be that if my fiance comes in through U4U, we marry, but she wouldn't be allowed to adjust her status due to being paroled in the US. I could also see this being perceived as "preconceived intent", and thus her adjust of status could be denied. Then she would have to go back home after parole ends, and that time would have been better spent going through the I-129F/K1 process.