I just read that sentence, and it doesn't explain anything. It just says they're not what he likes, so here's another one that might work: http://www.mucommander.com/
The separator of TotalFinder and Xtrafinder is just too thin. I want to see right away which side is in focus. When you click on one of the two windows the other one becomes washed and is also covered by the shadow of the active one.
I read the article. I stand by my suggestion. The writer does not present an argument against those existing products. This is Wheel 2.0. Stop the pain. Contribute to software that exists.