There is no doubt there was an element of triple option in Osborne's offense. I think where writers and others lose this argument is that it wasn't the main staple. By saying there was an element of the triple option, I could just as easily say there was a passing game element to his offenses as well, but I wouldn't classify Osborne's 80's and 90's teams as passing teams.
The Osborne offense was a power run, I formation offense, that used a mobile QB in option runs on occasion. Many of the concepts were not necessarily unique to Osborne. He was able to combine different concepts and play calls to keep defenses off balance. Many other coaches have tried to use aspects of his offense with less success. If it was simply the offense, everyone would run it. But it wasn't simply the offense. Turner Gill, Frank Solich, were around Osborne for 30 years, yet their teams didn't have the success that Osborne's teams did, even running similar concepts. If Tom Osborne wanted to run the wishbone, he would have been successful running the wishbone. If he wanted to continue to run a Pro Style offense, he would have continued to be successful.
Bottom line, the offense didn't make Nebraska a successful team, the coach did.