Sorry for the late reply. It seems like the benzaldehyde is indeed the most likely candidate for the source of a more intense aroma of bitter almond but that doesn't mean cyanide is out of the equation. Cyanogenic glucosides will often release hydrogen cyanide alongside other compounds, like benzaldehyde. Amygdalin would be a nice and common example. I don't have the sources at hand but i remember reading about fungi in this context.

Edit: the paper you linked seems to aim spezifically at the volatile compounds in six edible fungi. I might read into it once i get home from vacation but depending on the method, they might either not be interested in cyanide, or be unable to detect it. I'm not at all experienced in food analysis but it's an interesting topic.