I remember this as well. I'm pretty sure one of those pilots killed was our Korean War top Ace, Capt. Joseph McConnell. They didn't tell him the outcome of his actions as I recall.
Considering that many war time Merlins had their time to overhaul changed (shortened) by the number of times and/or the time spent at high boost ratings (as noted in log books) I don't know why it would come as a surprise that engines used for racing would have a shorter life.
Nobody expects Nascar race engines to last 100,000 miles