I suspect you've never driven an older vehicle with the shifter on the steering column.
Or a new Mercedes ;)
I've engaged my wipers when meaning to shift gears before, in my truck which has a steering column shifter. After driving the truck for years. I have ADHD and I very often let my brain go on autopilot for things I do every day, and sometimes it just does the wrong thing. It doesn't matter how complicated or "intentional" the task has to be: my brain will memorize it to the point that it can execute it on its own without me consciously thinking about it.
I think it's totally plausible it was a muscle memory thing, if the at-fault pilot's brain works anything like mine.
(Side note: I actually took some flying lessons, including going through all of ground school, and realized that my brain is just not cut out for flying. I am the type of person to "cowboy" things if I feel like they're not worth doing, and flying is an activity where the tiniest missed checklist item can result in death, so I realized I have a statistically high likelihood of crashing due to some boneheaded mistake, and stopped taking lessons.)
Everyone in this thread thinking “these actions are temporally and physically distinct and therefore impossible for anyone to confuse” isn’t really thinking about the problem the right way. It’s not that I’m actually confusing two actions. It’s that I’m accidentally allowing my brain to perform one action when I meant to let it perform another action. “Allowing” is an important word here, because it illustrates that my brain is capable of doing this on its own without me thinking about it, and often will do it on its own, if I let it.
This could be anything: starting a car, taking off a medicine cap, typing my password, clicking around cookie warnings. If I have to do it repeatedly, my brain will be able to perform it subconsciously, and I will do it without realizing it.
For fuel cutoff switches, it doesn’t matter that there two of them in a row. If you cut off both of them every single time, and you fly every day, your brain is gonna automate that task.