Can confirm, I spent that long in a coach seat on the California Zephyr from Chicago to Reno. I wouldn't exactly call it world-class comfort to sleep under such conditions, and I wouldn't recommend it to someone with a bad back, but I've slept in far worse (but then again, I'm a weirdo).

The main downside for coach is that post pandemic they don’t have access to the dining car.

They still aren’t offering access, and at this point, it doesn’t seem like it will return.

You’re limited to what you bring with you, or the snack car which is essentially a vending machine

Probably good to mention that (at least on the trip I took), the coach seats have a leg rest you can pull up for almost a recliner-style experience.