I did the test with the latest versions available at the time, so that must have been with 2.6.0.
I redid a test with the current dev build, and just Distant Terrain 2.6.0, simply riding horse in the desert, see logs in attachment.
GC takes less time, 40~45ms, maybe because unmoded resources are lighter. But GC is still triggered with each new map pixel.
Last one in the log is triggered by the closing of the "Escape" menu when I used it to exit the game, but this one is well identified (called from UserInterfaceWindow.CloseWindow() )