You're flatly wrong.
That's exactly what happened to me when I bought D&D for the first time. AD&D 2E had just come out. That wasn't just "not a secret", it was downright advertised - but I wasn't already inside the hobby, I wasn't reading magazines or browsing forums. I went straight into a Games Workshop store (as was the fashion at the time) and bought "AD&D" - and a couple of weeks later when I showed it to a friend he was like "You've bought the wrong edition!" - so I got an early taste of edition warring!
Anyway, this still happens. Absolutely normal people, new to the hobby DO walk into shops and just pick up "D&D". This is absolutely a thing and pretending it isn't shows that you're out-of-touch with how the a significant proportion of people got into this game in 5E, which wasn't through deep knowledge and careful research, but just becoming aware of D&D and going and buying it. The first new-to-5E group I DM'd for had done exactly what you're denying happens! They didn't really understand what they'd bought and through a friend of a friend I was asked to come and DM for them one time to get them started.