Tesla can lower performance for a test drive on a performance EV to match a slower model. I wonder if they plan to add a Model 3 mode to their Model S test drive vehicles? That would allow some early purchasers to test the feel of Model 3 acceleration. If the customer isn't satisfied, then crank up the power and upsell the customer to Model S.
I believe car dealers in general would prefer you test drive the most powerful and fully loaded car on the lot, regardless of what you want to buy. Later, when you actually drive the one you wanted, it will be a much less satisfying experience, making for an easier upsell from the very beginning.
I just had this happen at a MINI dealer. My wife wanted to test drive a regular Cooper S to feel the difference between S and non-S. But the salesguy spent 10m trying to get the the car with the performance upgrades (JCW version) off of the dealer's sidewalk area so we could drive that one instead, insisting that it was "pretty much the same" (it is sooo not-the-same). After that, my wife stopped talking regular Cooper and only Cooper S.