Larry doesn't ever see the units he sells for the most part. The factory ships to a warehouse, the warehouse ships to you. If it is factory error, you can't blame larry for that, really. Also, you can still plug the 6 pin into the four pin, it won't make a difference, so you should be good. You shouldn't have had to cut it.
And the fact that he offered return/replacement is good, not bad. Larry is most definitely not a donkey-hole, having catered to this forums whims for years now. Every time I've had an issue with his products, he's done everything he can to get me up and going again.
Please remember that people like him are for the most part a one-man show, and it's not easy being engineering and customer support simultaneously.
We're all human; mistakes happen! And that's OK!