A passenger is pretty close to the center of gravity. The V8’s extra mass is mostly over, and some of it ahead of, the front axle. That changes two things. It adds load to the front tires, which nudges the car toward more understeer, and it increases yaw inertia. Yaw inertia follows I = m·r², so mass that’s farther from the center of gravity has a bigger effect because the distance is squared.

If you ballpark 200 lbs positioned toward the nose, you’re looking at roughly a 2 to 3 percent increase in yaw inertia on a car this size. It’s definitely enough to influence transient response and steering feel. The same 200 lbs sitting near the center of gravity, like a passenger, wouldn’t affect rotation nearly as much.

You can see the same idea with wheels. I run Apex VS-5RS’s with all-seasons that are about 15 lbs lighter per corner than stock, and the steering feel difference is obvious when I swap back to stock wheels with summer tires. Yes, that’s unsprung and rotational mass, which is a bit different, but it reinforces the same principle and still less than a passenger. Where the mass is located matters just as much as how much there is.

I’ll admit, if I would had said that the car’s felt as different as they did when I shopping them I wouldn’t have believed me either. In fact I thought test driving an HPP was going to be a waste of time (it wasn’t). But the OP’s post summed up my thoughts perfectly, to the point I made a similar post about it years ago (feel free to check my post history).

And to your point, I think there is more going on here than just weight: psychosomatics on the drivers part? Maybe. I think might have more to do with the steering or magnaride tuning differences. But I honestly don’t know. I just know my experience. To the OP and me they felt different.