There's probably some truth to that, but the even bigger reason was lack of depth. After Dormady transferred, there would've been a steep drop-off at 2nd String QB without Chryst. Chryst was a good option because he was familiar with a pro-style offense, could immediately compete for the starting job, and could add depth.
While Shrout has a great arm and shows some promise, he's not ready yet. If we're in a situation where we're starting Shrout this year, it basically means we're sacrificing this season for the future. And McBride is the only QB on the roster who is truly a "Spread QB"; and really a "Spread QB" at a G5 or FCS school. I'm very skeptical of the idea that he can fit in a Pro-Style offense or that he could start in the SEC.
Given that, I think we'd be in a pretty awful situation without Chryst, regardless of whether or not he wins the starting job.