[floatingatoll]

Any time someone says "this is xyz 101, how could anyone be so confused", I hear instead "the human capacity for doing something without what others view as 'minimum sufficient education to survive it' remains unchanged throughout human history", which is precisely why the warnings are so dire. It's not to scare people away, it's just to offer them a defense versus their own curiosity and impulsiveness until they choose to make time to learn xyz 101.

[alecst]

I guess... I mean, it is more mysterious than you suggest, given that this fellow had been foraging for 10 years apparently.

It's like a driver mixing up the gas and the brake pedal. I don't really have an explanation.

[floatingatoll]

Ah! That sounds like a job for an NTSB-type analysis, because most human WTFs are built on a series of improbable events.

Maybe their glasses were fogged? Maybe the afternoon light was at the right angle to hide the 'gills' enough that their check failed? Maybe they had a time-efficient shortcut that finally found an edge case they hadn't planned for?