“You are saying that some am haaratzim decided not to duchan, the rabbonim didn’t stop them, and later generations lied and said there was a reason, but we can see right through them, because we know the reason they give doesn’t make sense..”
Even if that was what I was saying (though Id phrase it differently).
I’m still not sure we are arguing
Bottom line is There is no HALACHIC problem with duchaning today (do you argue on this point?).
Nonetheless, we dont duchan, because in spite of there not being a (good) reason not to duchan. We follow our minhag.
This is my point that a minhag can override halacha (within certain parameters of course) just like in the Magen Avraham YOU cited earlier