Honestly, he could. And here's my working theory right now:
North American hockey is a bit of a mess right now, and there's a lot of uncertainty.
I think you're going to have quite a few top prospects on loan next season, and I think there's a good chance that teams proceed conservatively. In other words, unless a kid is a high proability to make the roster, they probably just leave them be or loan them out for the season. I don't think you're looking at teams really desiring to shuttle guys back and forth, or break their bubbles more than they have to.
This approach could very much impact guys like Reunanen and Miller. They're right on the cusp, and they could make the squad. But I don't think it's considered a "given" at this point. And if the Rangers even suspect that either guy might need more time to cook, they may very well just prefer to let that happen rather than forcing the issue. Otherwise, guys like Miller, Reunanen and Robertson were all guys who could've potentially gotten long looks this season.
Johnson isn't a good player at all, he's barely an NHL player at this point. But he's cheap, he's familiar to the defensive coach, and he can stay with them the entire time if need be. To me, he's Mr. Right Now.