Good post- thanks for sharing.
I agree it's a good question- most are good with it, some could have need the post season before discussing this, and others- just don't feel the way you do.
My thoughts- you don't pull the trigger on a trade like this if you don't plan on using him at all. I think that Osh was going to use him, just maybe not in the way he has been so far- it's just something that evolved from Strev becoming ineffective and Zach coming in and doing much better than expected and here we are now.
Osh has been loyal to his QBs and players almost to a fault- this I agree with. It's the way he coaches- and there are more pros than cons to his coaching philosophy. I think we are seeing a break away from his die hard loyalty to players and going with what is better for the team- does having ZC in @ starting QB outweigh fostering confidence in your original starter on the cusp of a playoff run? I think it does. Has Osh learned from past mistakes? I think so. Does he actually have an "better" option in ZC than past years? I would argue: yes. I think all of these things are playing a part in why Osh is breaking from his past pattern of player "loyalty or die!".
Quick answer- yes, I think Osh totally planned on playing ZC, but he did it in a very analytical way by taking in all the angles as things progressed and the result is what we have now.