I don't think that's what the OP is saying.

At most checkpoints, there's a line to get to the TDC, and then once you get past the TDC, there's one or more lines to get through the x-ray/WTMD equipment. If those lines have backed up to the TDC, by default the TDC is shut down, because there's no place for a passenger to go once their ID has been checked. It's not a matter of the TDC slowing things down; it's a matter of the "real" screening going so slowly as to fill the pipeline between there and the TDC.