Spyglass not going all the way up in third person

I discovered this entirely by accident, but As you can see from the screenshots I've taken, the spyglass doesn't fully go up when looking up in third-person mode. I don't know if this is actually a bug, or if it was just an oversight in the programming.

either way, it does bug me quite a bit, so...... if anyone can explain this, that would be greatly appreciated 

thanks for reading