So, the new outfield dimensions and the new construction may be one big thing going on.
I know they tried to keep the changes mostly "neutral" with the wall coming in and out, up and down in various places. But things like closing off the way air flows into the tunnel might actually end up being a significant reduction in the HR park factor.
I would say that we need to watch it for a few years to really know but they are making more changes this offseason and the reduction of foul territory should make a significant improvement for hitters so we will never really "know".
But the 2023 statcast park factors for RC show a 98 park factor overall and a 92 for home runs.