Ahh interesting! Ive never seen or heard of a car manufacturer putting the backup camera screen in the rearview mirror (probably bc, for the reasons you mentioned it's a terrible idea!)
Backup cameras weren't required in vehicles until (i think) 2018. My guess is that (similar to banning popup headlights), it was only required for new vehicle models released. The 370z had a ridiculously long production run starting in 2008, so they weren't required to put one in
I've got two of the P2415Q's and will probably keep using them until they kick the dust. Every 6 months or so I look at monitors and anything with an equivalent or higher DPI is too expensive for me to justify ($1200+ per monitor)
This is why I've stuck with my pair of older 24" 4k dell monitors.
Before them I was using regular 2k monitors, and would get headaches staring at a monitor for a full workday 8-10 hours and my eyes were so strained I usually ended up just going to bed right afterwards. I've never used an ultrawide, but I'd be really interested in trying one out IF I can get a similar PPI (~192 or higher)