i guess you should ask a Zen practitioner about this koan! Personally, it seems to be a focus on the 'now', though as i understand it, the Vajrayana tradition advises us to not focus on our physical needs so if we look at this koan in a literal sense, it would be contradictory. I mean that if we are hungry, we don't necessarily have to eat
now or if we are tired, we do not necessarily have to sleep
now as these physical needs are all in the mind, which is often deluded. Often when we think we are tired, we are not as tired as we think (does that make sense!)
Anyway, if you do find out what a zen practitioner thinks of this koan, do let me know.