Well, the idea is that there comes a time when any intermixture with the spiritual light ceases.  That would be my speculation.  I'm anticipating the event proclaimed by the Buddha:

It is liberated . . . birth is exhausted, the Holy Life has been lived out, what was to be done has been done, there is no more to come . . .' 

Not necessarily in this life!

My  Buddhist teacher said that when one gets nibanna, it does not involve going anywhere or becoming anyone. There is also the analogy of attaining arahantship as being like a flame that fades out.  

I agree that traditional definitions of these types of experiences often fall short and tend to limit what may actually be a genuine supramundane experience.  It certainly is inspiring and gives all the impetus to continue the practice, come what may!