I've been playing with the latest Mac MatterControl and just noticed that it doesn't actually seem to set the temperature (at least, not if you're just doing a straight gcode export -- MC isn't plugged directly into my Kossel Pro).

In reading through the gcode, the only temperature commands I see (M104, M109, M140) are the ones from my own manually-configured start/end gcode. These values differ significantly from the values I set for my filament, so it's pretty easy to tell.

Yep, you'll want to use the placeholder variables in your start/end GCode as whosawhatsis linked to: https://github.com/MatterHackers/MatterControl/issues/51