In the same way, saying that the wood is better because it was boiled isn't right either. The reason given to boil water is to kill parasites -- but if there aren't any parasites in the first place -- then there needs to be another reason why boiling is needed. Otherwise, it is just another ritual/"magic words" things that maybe indeed does make you feel better, but isn't necessary.
I disagree with this.. boiling may not be necessary but it sure wont hurt, especially if the wood comes direct from a lake, river etc. you never know what is living on/in it. Boiling will also leech tannins faster so that is a bonus if you are not after that look.
boiling big wood is a problem,but anything that can fit in a big enough pot could be boiled. i boiled my piece thats in my five gallon, it seems like the safe thing to do. Remember we are careful and try to use stuff that has not been used with any cleaners/chemicals, stuff like our buckets, brushes etc, the things we use for tank maintenance. So why not boil something that will go in with our fishes.
Getting back to the wood in question that supposedly killed all the fish, the fact that it never leeched tannins and is supposed to be bogwood makes me suspicious. As was said earlier maybe it was not suited for a tank, or had sap in it that was toxic. I'm betting that some chemical got on it somewhere, perhaps in the store.