NCE is probably recommending it for less than 5 amp systems due to the size of the supplied feeders.
If you are using your MRC system with electronic circuit breakers, which would lower the available current before tripping, to less than 5 amps. Doing something like this has always been my recommendation. Eight amps is a lot for a short in an HO system, so electronic circuit breakers are advisable. Or set your MRC to output no more than 5 amps.
Even then, it is a good idea to use electronic circuit breakers with trip points set to say 2.5 - 3 amps for HO. You are trying to run trains, not weld!
However you get below 5 amp max to your track, the NCE product should serve you well.
Wiring For DCC