Is it completely wrong? No.

Does it go to a place that shouldn't be adjusted until all efforts have been made with regard to the vacuum system? Yes.

If the vacuum system is not performing correctly, any adjustment to the modulator will be meaningless. Furthermore, you'll get yourself "lost" because the modulator has no defined position unless a pressure gauge is utilized.

The proper approach by Sun Valley should have been to set the modulator with a pressure gauge and then direct the owner/purchaser to adjust the vacuum to the modulator to correct any shift quality issues. But, Sun Valley doesn't want to address the vacuum adjustments because they probably don't know how to do it.