It does. Honestly, “self-taught sword fighters” are actually worse than untrained, in many modern cases, because they’ll pick up bad habits from TV, video games and other media.
The same thing applies to firearms, for that matter. You’ll see people trying to take cover behind car doors, drywall, or couches, only to get gunned down by trained professionals who understand that, no mater how nice the upholstery is, it won’t stop a bullet.
The biggest offenders I tend to see with swords is unnecessary flourishes and strikes that leave the attacker open to quick counters. But my training with swords is extremely limited. So there’s probably stuff I’m seeing, but not recognizing.
Also, with swords, and other abandoned martial styles, what’s survived doesn’t hold a candle to the historical forms. Martial Arts that fall out of use get neglected, the populations drop, the preserved techniques dwindle, and the reasons behind those techniques get lost.
So, while there’s now a push to reconstruct medieval armed combat techniques, they’re in almost the same boat as anyone else who is trying to become a self-taught fighter. The training manuals alone aren’t enough, nor are multiple people trying to “figure it out” together. This is something most practitioners of the reconstructed arts will point out, if asked.