I think I solved this - it was brought to my attention in my misplaced PAPI wishlist thread. The touchdown zone (TDZ) elevation in the sim is 1253’, which far higher than the published 1181’. Further, there is a terrain “ramp” in the sim about 1500’ prior to runway 25, where it suddenly drops to ~1160.
That ramp does not exist in real life and it is a far more gentle (almost imperceptible) 20’ upslope beginning around 1160’ from the VOR (about .7nm from the approach end) to the threshold at 1181’. Not this ~75’ ramp that occurs over a 500’ distance.
I believe the Glideslope Antenna is set to the correct real-world height, but the terrain and resulting TDZ in the sim are too high, causing both a PAPI disagreement and a glideslope that is actually underground in the sim, resulting in a far too low threshold crossing height (TCH). Diagrams are in my thread, including the investigative work that led to the final conclusion.