I think that's fair. Use of Stiemsma, it looks, may be very situational. He didn't fare well against Hibbert, who was clearly too big and too strong for him. Also, being matched up with Okur seems to take away from his strengths, and Okur mostly stays around the three-point line. I also agree about energy.
But the thing is, we've always needed energy off the bench, so there's no harm to keep Stiemsma there. For one, less risk to be overmatched, and there are plenty of minutes to be had behind O'Neal.
I'm not sure why I keep arguing this, as I'm certainly not married to the idea of starting Stiemsa.
I just want to make a point about matching up with someone like Hibbert. Sure, Hibbert overpowered Stiemsa some, but really his advantage is that he has low post skills that are very rare for a big his size.
Again, there aren't a lot of guys like Hibbert out there. And, even for teams that have decent offensive low post bigs, very few feed the ball inside to the big on the block consistently. The dominant low post game isn't a big factor in the NBA these days. Even someone like Dwight Howard, the most dominant big in the game, is not a very good one on one low post player.
In the end, I'm happy starting JO and bringing Stiemsa off the bench for now. But, if JO continues to not produce, and Stiemsa continues to play well off the bench, I would certainly consider making this move.