What I stated is, the word 'pravrajya', for Sannyasam, is connected to Vyuththanam or Tyagam of Eshanas in the Upanishads like Brih Upanishad 4.4.22. And as I explained, this Vyuththanam is a giving up, due to an absence of interest or desire for children, wordly pleasures. The person is self content in Atman. Lack of energy does not come in the picture at all, as you can refer from the above passage (4.4.22).
Now, Vairagyam is a commonly used word for 'lack of desire/interest'' or detachment.
Due to the above upanishadic connection, I correlated Virajet to Vairagyam.
OK I will give an independent translation. Since I don't have Sankaracharya's Bhashyam with me right now, for a change I will give a translation provided by indological scholar Patrick Olivielle to the above passage. (Refer the book "Collected Essays 2") available online.
https://books.google.co.in/books?id=eoZlZprpSIYC&pg=PA212&lpg=PA212&dq=yad+ahar+eva&source=bl&ots=UFGuzUr_e9&sig=gDbX1gl5WlBPzJYDJsomMZBf1YE&hl=en&sa=X&ved=2ahUKEwjdtuGOlsncAhXLRo8KHZXaBe8Q6AEwAXoECAAQAQ#v=onepage&q=yad ahar eva&f=false
Translation:
Having completed the studentship, one should become a householder. Having become a householder, one should become a forest-hermit. Having become a forest-hermit(Vani), one should go forth (and become a Sannyasi).
Or else, one may go forth (into Sannyasa) directly from Brahmacharya, or from Garhasthya or from the Vana.
Otherwise, whether one is under a vow or not, whether one is a snataka or not, whether one has ceased to keep the sacred fires, or has always been without a sacred fire - on whatever day one becomes detached, that very day one should go forth.
Note that the last two lines are all-encompassing. They are all without exceptions, part of the same rule.
