Changing the light spectrum during flush

I have read some places it is good to change from HPS back to MH for the last few weeks of flowering. If so what benefits does this have or is it a waste of time. Those with experience please chime in.

Plants use energy to make trichomes to protect itself from uv rays. Some MH bulbs have a great amount of uv and some mh bulbs have as much as hps bulbs do. Just need to look for a MH bulb with a lot of uv. More UV, the more trichomes. So for the last couple weeks, since your bud won't be getting much bigger, it could only be better to add mh at the last couple weeks.

Only one person is familiar with this?