While Fred proves his method does work, most of us are tought that this shouldn't be done. Using a subdued light like Jerold does simply feels better. I havn't used BTZS tubes, but had good use of this piece of knowledge when "speeding up" the drain/fill sequence for a HP CombiPlan. (I lift the lid and drain the developer, just like pouring of the hot water from a saucepan with potatoes, holding the lid to keep the film holder in the tank. Then shortens this sequence by about a minute.)
I havn't done any actual measuring of b/f, but the negs sure look alright. If the light would have caused damage this damage shouldn't be even, but stronger on the outer sheets and on the top end of the films. The light I use is a normal yellow/green darkroom light. I do try to cover the tank/film from direct light.
Also, if I remember correctly, the older version of the web instructions explictly said "subdued light". (Before the YouTube days, the instructions was a series of pictures with text.)
//Björn