Many perspectives converge without crossing.
Indeed it does appear that the koan or hypothetical sort of question did give cues to the reply at least from the perspective of this supposed inquirer. I pay particular attention to the word "responsibility", and he is specific about the identity responsible, the doer of activities, even such as the noble path.
It is a powerful and loaded question for most transcendentalists. It is interesting that he is suggested to wait the next day to understand more about his own so nicely phrased statement.
The question refers to a certain level of spiritual development.
Not experiencing self in a natural way or in selflessness way, if it were possible and as a result from there "having" or living all possibilities has no practical basis as a statement for mere mortals. I can see how encouraging such a conception may be in theory, but master Thich Nhat Hanh not being a nihilist may be misexpressing himself on the qualities of the Brahman effulgence.
Such level may not become genuinely relevant prior to advanced mysticism. However, the statements though sounding remarkable don't appear to coalesce into a clear concept, and further, the work towards insight is postponed to the next day and pretty much returned to the asker.
I wonder if he'd also say that it is possible to exist without living, or to not exist without living or de-exist without death? And, if being human means anything or has any relevance as it pertains to salvation.