There's lots of foods that will make you sick if not cooked the right way. There's even more foods that will make you sick if you eat too much of them. Edible and poisonous aren't distinct circles in a Venn diagram.
Even if it's in there cyanide is pretty readily inactivated by the body because we have been dealing with it as a plant toxin to stop us from eating said plant forever. The issue is just avoiding a dose that overloads our own treatment system in the event we don't eliminate it through other means like heating.
There are other articles that claim the young plants contain cyanide, others that claim chopping the leaves causes the cyanide to break down.
I have been eating them for years without getting sick from them. On the other hand I know people who eat Amantia Muscaria mushrooms who seem to have suffered nothing worse than hallucinations and nausea.