I feel there are multiple descriptions of what Shikantaza is. I'm confused which one is accurate
Don't manipulate or control your awareness (attention) or any objects of awareness (breath, posture, mantra, present moment, emptiness etc...) in anyway. Let your awareness do whatever it needs to do. If your awareness/attention is caught up in thought, then that is where it needs to be at that moment. There is nothing wrong with it. Of course this doesn't mean we continue to think when we "realize we are caught up" (in other words, "the return happens"). If we continue to think, that will not be non-doing anymore. When the return happens, we just continue to sit. The important thing to remember here is that there is no preference given to "return" (or to being in the current moment) over getting lost in thoughts. It is complete no-preference sitting and trusting that awareness goes and does where it needs to go or what it needs to do. No manipulating or directing awareness. As Genpo Roshi says this essential non-doing and utter freedom of Shikantaza wears down the mind.
Sit and aim at returning to the present moment or posture. When you realize the present moment is not being attended to, then get back to the present moment or posture briefly and then continue to sit. We don't focus or try to stay on the posture or present moment. When "the return happens" we just briefly check the posture or attend to the current moment and then continue to sit silently. Zazen is not staying in the moment or with the posture but this returning again and again is itself Zazen.
Which one is the correct description and why do you think so?