I think he went a little hard on her. I mean props for uncovering this, but she seems only marginally at fault here, more for allowing claims to be made and not going out of her way to correct them, which really would be something one is unlikely to do when this was primarily a marketing exercise with stakes that are personally probably pretty high but for the world generally couldn't matter any less.
It mostly seems to be others that are misrepresenting her claims, some of which seem more truthfully described in her personal letter, which as a personal communication makes more of a vague reference to a single metric that can point to but not definitively prove a high typing speed.
Maybe it's just because she was old when all of this was happening and it's clouding my judgement but I think she was just a very fast typist and proud of it and when people wanted to use her as a spokesperson she could continue to take pride and make some money. I'm not sure I saw her outright lie during the video. She said Guiness World Records said she was the fastest typist in the world on the Dvorak keyboard. I'm not sure if it did say that, but it's an interesting distinction to make, maybe what Wikipedia would call weasel words nowadays. The level of seriousness this little marketing campaign would later be taken with is not something that could have been anticipated and it sounds like she got a pretty rough rubbing of her nose in the likely embellishment of the claims on the Letterman Show.
I don't know what my point is exactly, the video was excellently researched as far as my untrained eyes can tell and it really was entertaining, but something about the tone seems to lump Barbara in with more dedicated and sinister "cheaters" that Karl has dealt with on his channel whereas this really just seems more like a tall tale for a bit of fun that's mostly grounded in several truths, but which got stretched out of proportion and which Barbara seems to be left responsible for. The closing statement of the video seems to begin to make this point but makes it in a way that's more about the importance of proper research which implies more it's not her fault she lied it's their fault they believed her, whereas it seems more like, it's not her fault that other people lied and no one checked their lies.