I think the problem is Stroman's own brand of philosophy. I dont think Pete Walker or anyone else is encouraging him. I remember people were fapping to this article when it first came out, http://www.fangraphs.com/blogs/marcus-stroman-discovered-roy-halladays-sinker/
"Stroman started to use the sinker more often in his July 19 start against Texas, after finding a grip he was comfortable while fiddling around with a baseball at home."
“I have a sinker now, and it’s good,” Stroman said, proudly. “It’s a good pitch, and I get excited when I throw it. I get excited on the mound. It’s a pitch I started throwing like a month ago, and I’m already using it in games and having success with it.”
Marcus Stroman didn’t simply add a new pitch: he added, to his already broad repertoire, a pitch that compares well to a primary pitch thrown by a possible or probable Hall-of-Famer. And Stroman must’ve known immediately that he’d added something good.