On the basis that there is so much misinformation flying about regarding the failed coup then the only possible answer to your question is yes, he could be right. However, by the same logic, he could also be wrong
I don't think anyone disputes that the main protagonists involved were connected to Gulen, either directly or indirectly - some may have been members of FETO, some may not. Again, there is a lack of accurate information available and I suspect it'll be a long time before the actual truth about this failed coup enters the public domain, if it ever does.
Make no mistake, Gulen isnt a nice guy - in fact he's probably as much an Islamist as the wee fella. He's also a pretty clever bugger, his organisation turns over billions of USD every year which allows him to fund schools, colleges, universities and hospitals not just in Turkey, but all over the world. He's big in Pakistan I've heard and there's a bit of diplomatic wrangling going on between Ankara and Islamabad over his schools there - Pakistan doesn't class FETO as a terrorist organisation so they're saying we don't have a problem with the extremely generous Mr Gulen.
So, Gulen has power (FETO), he has money (lashings of it) and he's smart. In my opinion (and that of a few folks I work with) if Gulen decided to stage a coup then it'd be done right - not this half arsed attempt we observed the other week. When you look at the basic errors made by the "plotters", especially their failure to both capture the current regime and control the media, you have to wonder if it was ever meant to succeed...
JF