Do you mean 4-5g/L, or really just 4-5g? If you do actually mean 4-5g, you could get just as much hop character by waving the bag of hops near the fermenter!
That isn't dry hopping, that's hop tea. It'll give you a different character, especially if you're doing it with boiling water. The heat will isomerise and change of some the acids/oils in the hops. If you want to properly dry hop, chuck the hops straight in to the fermenter (doesn't matter if you go commando or in a hop sock), that's how actual dry hopping is done
Not only is this theory ridiculous, it's also incredibly insulting to the work of most brewers who make fantastic, highly hopped beers. No offense, but the content of your post suggests that you are quite a novice at brewing, so for you to make a baseless claim like that against great pro brewers is not only absurd, but also a bit laughable.
It certainly does show IBU differences for late boil hops - I'm not sure what makes you think that it doesn't.
And no, there isn't really any measurable scale available to the homebrewer that quantifies aroma (that I am aware of)
