Difficult (intellectually challenging) != hard work (back-breaking, sweat-inducting).

That's cherry-picking non-intersecting definitions though. Difficult can also be work that involves a lot of physical or mental effort, not necessarily confined to just intellectually challenging. Hard work can also refer to work that requires mental effort or mental stamina, and does not only refer to highly physical labor.

That is indeed cherry-picking, and was my intent. Bluntly, most devs I ask about their lack of ability in the security space think they're not smart enough to get it right, so don't even bother to try.