Well I haven't read the article you mentioned but I've ordered the back issue and it'll be interesting to compare the two. Until then what evidence did they offer?
The older article had some accounts, anecdotes, and observations that can credibly confirm there were Black Confederates. The real debate is how many there were since many records, muster rolls, etc were destroyed, lost, disappeared.
I believe it's likely there were more black regiments than officially recognized. I've met several descendants of black confederates and the stories handed down are amazing.