You raise an important point
@swenpaylay and I'm grateful for your reply. A tire choice is a balance of compromises between various capabilities and limitations and each driver needs to weigh the style of driving they encounter against the strengths and weaknesses of the tire they select.
Nitto does an admirable job of disclosing the strengths and weaknesses of their offerings. Here is the chart for the Ridge Grappler:
View attachment 2703
Terra Grappler G2:
View attachment 2705
and the NT421Q Premier All Season Crossover/SUV Tire:
View attachment 2707
Your experience is certainly consistent with their claims and is definitely something that must be taken into account when selecting a tire. For my usage (primarily Southern California highway driving with weekend soft-roading excursions), the slight decrease in on-road performance is worth the increase in off-road capability. Obviously these charts need to be taken with a grain of salt as they don't indicate any actual hard data and can't be used to compare to another manufacturer but for comparing the different Nitto tires relative to each other, I find them helpful in understanding what the trade offs will be.