Isn't this valuable information that can be used to achieve a purpose ?
Yes, to a point. If you left the VNAV in, instead of using the ILS GS (discounting RNP approaches), where would you end up? And that is using database waypoints. As soon as you start putting in relatively inaccurate data rounded to the nearest 100ft eg VRs, the accuracy of the box diminishes. It's all rather academic outside 300ft but below that, an approach path/profile inaccuracy will be more obvious from looking out the front than by what the FMS is telling you.
The only system that is designed and trusted to take us to touchdown is the ILS GS. Everything else requires pilot control, because it is not accurate enough. Because of the potential inaccuracy (in my machine, every day it's hot the database profile is at least 50ft too high - nice at 200ft eh!) IMO you're better off chucking it all out the window and visually flying down "the picture" from 500ft or so. If you've got a flight path marker, then well and good, although using it is a bit like "reverse logic". Pick your normal spot on the windscreen (oh for a HUD) and down you go.
Of course, this is all academic if you have a temporary PAPI. Add 300ft/nm to a close-in waypoint eg runway-2nm and from there, look out the window and fly down the lights.
