Humans adapt pretty darn quickly. It wouldnt take you very long to get used to it. In fact, You would probably adapt in a day or two, much less if you ever drove a manual transmission anything (car, motorcycle, etc), anything where you had to shift gears and had engine braking.
You would adapt, because the feeling of deceleration if you take your foot completely off the accelerator would be enough to feel like you were learning to drive a stickshift vehicle. With that being said, a 30 minute test drive is not long enough to adapt.
My wife almost never drives my car, and drives by "pulsing" the accelerator as I mentioned. Also as I mentioned, a lot of people dont realize they do this, but the first time they drive a stick (or a car with regen braking like tesla or any other EV that has it) they will quickly realize that they "puuusshhhh" on the accelerator, then take their foot completely off to cost, then "puuuushhhh" then completely off, repeatedly.
Next time you get in your regular car, pay attention and see if you or your significant other drive like that.
I agree. On my test drive, I hated the regenerative braking and had the Tesla rep turn it off for my test drive. I understood it was good if I could get used to it though, so I left it turned on when I got my M3. It took about one day of driving to get used it. Now, when I drive my wife's ICE SUV, it feels dangerous and out of control when I release the accelerator and the truck barely slows down. It feels like a runaway train.
One pedal driving is one of my favorite features of the M3. I believe it is much safer also. I once had someone pull out in front of me and in the split second between taking my foot off the accelerator and pressing on the brake, the car had already slowed down significantly. I believe it helps stop the car much quicker in an emergency situation like that.