I was confused by the 1st Minnesota's inclusion as well. That unit willingly charged into near certain death and was shot to ribbons. How do you overrate 82% casualties? It is still the highest casualty rate ever suffered by any U.S. Army unit in a single engagement.
Unless he's making the argument that the 1st Minnesota's charge wasn't as instrumental in holding Cemetery Ridge as often claimed, or that Hancock erred in his order. I'm not sure I'd agree but wouldn't dismiss it without having first read his argument and considered whether or not it is well sourced.
I fully agree with the 20th Maine's inclusion, though I'd bump them up to the #1 spot. Little Round Top and the 20th Maine aren't only the most overrated aspects of Gettysburg history, the stand of the 20th Maine is arguably the most overrated action by a Union regiment in the entire Civil War. More people get their history from Hollywood than books, and so the average viewer of the Gettysburg film probably thinks Chamberlain and the 20th Maine won the battle or that Little Round Top saw the most critical fighting of the 2nd day at Gettysburg, neither of which is true. That probably goes for the average visitor to Gettysburg as well, who is much more likely to spend more time on LRT than the Wheatfield or Culp's Hill, for instance.
Having said that, I know I'm going to ruffle some feathers by saying the 20th Maine is overrated. So let me be clear: Saying something is overrated doesn't necessarily mean it is bad or unworthy of praise. It just means the hype exceeds the reality. All of the men in the 20th Maine were heroes. LRT just wasn't as crucial to the battle's outcome as some of the actions on other corners of the battlefield on the 2nd Day, and there were other Union units who were just as brave or faced greater odds than the 20th Maine, but are much less well known.