Make no mistake. Telling the media that Bowey needs to prove to him that he deserves to play because he hasn't so far. That he needs to get the mistakes out of his game. Saying that was a choice. There are a lot of diplomatic ways to side step that question. As is done all the time.
I thought the way he phrased it all was a nice balance between diplomatic, honest and forthcoming. He didn't dodge the question, like he has been with DSP's conditioning issue, but he didn't trash the player or throw him under any sort of bus. He probably told the player the exact same thing he told the media, there's no reason on earth why he would have told Bowey in private anything different.
And to the rest of your post, yeah I tend to think TR knows what he has with Bowey at this point, is a little disappointed that he hasn't taken another step, and I agree with you that he's had the opportunity but at least two other players appear to have jumped right over him. But I disagree that his public comments were inappropriate or improper or should have been kept private.
Its up to the coaching staff to get the most out of every player. TR hasn't head coached a single NHL game yet so I'll cut him some slack on Bowey's development stall at this point, given that other players that TR has coached directly (Dmen) are showing very nice improvement and solid development. Not every prospect takes that final step, obviously, and maybe TR is running out of ways privately to find Bowey's next gear?