We should take nothing away from the professionals who wrote all those pubs, with 99% of the info as solid and helpful (and even the VRS info is conservative, thus safe). The thing we must do is seek the "why" for things, becuase our procedures wil be tied then to understanding, not just rote memorizing.
I truth, if you have more than 300 fpm downward rate while below 30 knots, you are making a lousey approach, VRS or not! My personal gate is to be less than -300 fpm when below 150 feet and 30 knots, just for basic power conservation, since the collective pitch suck-in can be 10% above the hover power if you make a hairy flare when entering the hover.
VRS can't occur at less than 70% of the downwash velocity, which is perhaps 700FPM for many light helos. If you set -300 fpm from a hover, and let the aircraft settle without raising the collective, it will accelerate downward (that is not VRS) until it gets into VRS at maybe 700 fpm. most professional helo pilots who do photo chase and the like have made vertical descents like that without fear of VRS (and rightly so). The book is not right, but as advice for newbies, it is sound advice.