I had a couple with spring loaded "crash damage", one on the side and one on the rear. When it got hit hard enough, the panel would flip around and the car would be "dented".
They still make them. Still metal too. My 3 year old has a few and loves them. I have some old ones and they still work, albeit not as fast as they used to.
This seems accurate to what modern car underbodies look like, a smooth underbody is very important for aerodynamics and therefore fuel efficiency. For race cars it is often even more important not only for fuel efficiency but for downforce.
Well now wait a minute, the Corvette on top may be correct. The car manufacturer puts so many covers on the bottom of cars now the hot wheels might be accurate.
Hot wheels from the 70s and 80s were deadly weapons ... you stepped on one it was like stepping on a roller skate, you broke one it turned into knife and if you threw one, you could cause a concussion. Even just opening up one of those damned things when you were kid usually meant you severely cut yourself (I know from experience).
I have one or two hot wheels shaped wounds somewhere on my skull from when my brothers tossed these things at me in a fight .... and I returned the favor as well.
For anyone looking for a fun way to play with your toy cars, I highly recommend the free tabletop game GASLANDS. Glue some guns to them and blow them up with your friends!
Some hypercars actually have a flat undercarriage to maximize aerodynamics. Also not all HotWheels are depicting real cars, so they might not have realistic underbody. This could be one of those 2 cases.