Does the Torque Converter heat engine while idling??

yes. But perhaps not for the reason you might suspect.
In park all fluid pressure except the small lube line is dumped to the pan.
In Neutral the torque convertor is filled.
And in Drive, the forward clutch is engaged, so the TC is trying to move the car. But with the brakes applied, it cannot.So the TC does what it was designed to do;it slips. This heats up the oil. The pump sends the hot oil to the rad to be cooled by the water flowing all around the internal cooler. And the water temp. rises, as the oil cools.
Furthermore the reduced idle speed slows down the waterpump, and the connected fan. This reduces the air speed/flow through the rad, slowing the cooling rate. You might think that 175 rpm is nothing, but consider that 175/850 is nearly 21%.