PEI 3721, I agree, that EGPWS has to work accordance with this algoritm. But....
Two signals are sent at the input to the Geometric Height, - the radio altimeter and GPS.
I suppouse, that in this region there was a reception of differential corrections (WAAS or other)
through the geostationary satellite POR 140 degrees.
In this case GPS altitude will be used. In database of EGPWS is WGS-84, but in this region the Indonesian datum is used and the
height difference is 22.99 meters.
Those. the EGPWS system considered a different relief than the actual one.
I suppose that with the ATR-72 the same situation (the difference in altitude is 30 meters)