I would say that - all things being equal - you need to increase the flavoring in high VG liquids to get the same intensity of flavor.
But most people go to higher VG liquids when they change their delivery system in some way - maybe going from a Nautilus to a Subtank or an Atlantis to a dripper. Generally it's from a less powerful system to a more powerful system. In those cases, you're actually changing several things at the same time and it can be hard to determine exactly what is making a flavor change.
Also, different flavors behave differently. I have a house flavor (50/50) that uses canteloupe, strawberry and raspberry. In the high VG version, I had to increase the raspberry flavoring by 40%, the strawberry by 20%, and the canteloupe not at all. I don't know if the flavors just don't carry as well in the higher VG or do they just not come across as well at higher temperatures.
And some flavors don't come across at all in high VG/high temp. My favorite flavor (a coffee) is absolutely wonderful in my egrip at 1.5ohms but tastes like dishwater in drippers or sub-ohm tanks. I also feel most custards only shine in sub-ohm builds.
And steeping can make a huge difference. Maybe no on simple single-note juice but I firmly believe that more complex liquids need to not just steep but also need an airing-out period (to let any alcohols in the flavorings evaporate away).