Your actions don't require reasons, just try stuff out and see.
I began today, like every day, by reading a chapter of the bible. No not The Bible, I mean Zen and the Art of Mixing by Mixerman. He makes an interesting point about the folly of explaining your reasons behind any request.
Suppose for instance you felt that your singer could emote more in the second chorus. So you tell them this and explain exactly why you want it so.
You hit the record button and the singer emotes, just as you asked, and for reasons that you just explained.
The trouble is that now that you have heard it, you realize that you don't like it like that. A plain and simple delivery is better.
Now you have the difficulty of telling the singer that not only were you wrong, your reasons were wrong too. Perhaps the reasons for wanting a plain and simple delivery will be wrong as well.
Or perhaps rather than change your mind, you'll stick with your reasoning, which privately you know is wrong.
This is hardly the way to produce great recordings.
When you're working with musicians, you don't generally need a reason for anything. If they respect you, due to the good work you have done in the past, or simply because they are taking direction the way a good musician should, they'll just do what you suggest. So you can try a few things out and see what works best. Whatever works best musically doesn't usually need a reason spelled out in words.
The exception to this is if you are giving a singer motivation. If they don't understand what a line means, for example, you could explain it for them so they can interpret it better.
It is often forgotten, particularly on the Internet, that good production is more about music than it is about equipment, and this is an excellent example.