as a counter-data point, my previous car had a DIY hard drive mp3 player install; it dated back to when notebook drives were still 40 pin IDE and 80gb was the largest you could get. somewhere around 2003 timeframe, I think. I had the hard drive in the worst position (rear corner of trunk) and you know - for 15 or so years, I never had that disk crash or lose music data (that I could notice). 15 years of hot and cold (ok, bay area, so not too extreme) cycles and bouncy roads, potholes, etc.
now, that said, they don't build spinning disks as well as they used to (isn't that always the trend?). I doubt you'll get that much life from today's spinning rust drives, but it does show that that tech *can* work fine in a car, even without any special shock mounting; just some foam I had. I basically threw this HD player in the trunk, never had to touch it in all those years and removed it when I sold the car, just half a year ago.
Yeah there are special HDDs made for this sort of thing to that you could probably use without issue. But they tend to be quite bulky and expensive compared to an equivalent SSD.