They never figured out what happened at Tahquitz. I believe there was a cordelette attached to someone but they aren't sure whether the gear was even in the rock at the time of the fall. The final report, I believe, suggested that they fell from somewhere between their supposed route and the rap off but friends of the guy who had the gear still attached to him said he wouldn't have walked around without cleaning it up.
Yes, the Gunks are different in some ways. I'd trust any single well-placed piece at the Gunks. The other two pieces are in case I've made a mistake in either technique or judgement. Based on current thinking, if I were somewhere building an anchor I really didn't trust, I'd put more thought into how I was equalizing it.
Mainly, I feel that if cordelette technique were dangerous it would be supremely obvious by now from the accidents that would have occurred. That's how I feel about the EDK too. You can run as many tests as you want but real life is telling us that both techniques work fine and since they're convenient and familiar, I'm going to keep using them.