Dies are not always changed in pairs so changing a reverse and not the obverse does not surprise me. What needs explanation is why are there only three die varieties? These were NOT the result of just changing out a die witht he wrong one. These coins were struck on a quad die press (four obv and four rev) and at least three of the reverse dies were swapped out for quarter dies (There are three die pairs known). Now if you are swapping out the dies and you install four anvil dies and then say go to lunch, it could be conceivable that you come back and forget to swap out the hammer dies. But then there should be FOUR die varieties. So where is number 4? If this was an accident it seems highly unlikely that the die setter would not notice when he was setting the anvil dies that the press had three quarter die and one dollar die staring up at him. If done deliberately on the other hand, why swap out three dies?
I for one have always hated "fantasy issues" like this that look like a mint employee wanted to supplement his income. I hate 1913 LHNs as well. Since errors are so easily created in the mint, I have never been interested in paying extra for a defective or fantasy product. To each his own I guess. If I wished to collect errors, I would concentrate on the errors viewed as most likely to occur, not such things like this.