Wow, didn't know there was a name for this. I accidentally did this when i had a defective cob glowing for a 2-3 hours after lights-out and a large area of nanners under it by ~mid flower. I just cut the tops off with nanners. The response from the plant in this area was hard to ignore... I took off some large chunks, too.
When you are certain any remnants of vegetative growth is done -- i.e. no more leaves, no more vertical growth etc... Although with so little information out there, it's just a guess when it comes to anecdotal evidence.
There's likely an optimal amount you want to take off, too... too little and likely no response...
None of this considers the risk of the stress... on a sensitive plant you might end up with nanners all over.