Assuming TCMA works as intended, it does eliminate the risk of uncommanded/uncontrolled high thrust (UHT) on the ground. There is still some risk that UHT could happen in the air during final approach - if you're less than ~100 ft. it could be pretty exciting. It's shown to be controllable, but the pilot does need to be paying attention and fly the aircraft or it could end badly. The good news is that the exposure is maybe 30 seconds per flight, and the probability of UHT is something between one in 10 million and one in 100 million flight hours, so the odds of it happening during final are astronomically high. However UHT can be caused by a single failure so we need to show it's controllable (ref 25.901(c) and 25.1309 - you can't use probability arguments for single failures that are catastrophic).