"Crimes of the Tribunal" (T_Bk_CrimesOfTriTR) reads thusly:

"The ascent of the mortal gods, however, uprooted the system and destroyed the old ways. By utilizing a position of leadership in the battle against Dagoth Ur, the Tribunes slew the savior, the victor of Red Mountain. They robbed the Heart of its powers not meant for Man or Mer, and in doing so, they conjured the Devil into this world. But, such a creation was necessary for the fledgling gods to assume control."

Even "Progress of Truth" only states that the Tribunal's power may have come from Red Mountain, and the Heart of Lorkhan isn't mentioned at all. "Crimes of the Tribunal" is publicly stating far more than should be public knowledge at the time of TESIII.