I'd disagree, I have a 16" 2021 MacBook that has the XDR Display with 1000avg/1600peak brightness and I constantly have it maxed.
It's very annoying have it next to my BenQ 4K monitor that feels so much flatter in comparison. It just makes any other monitor so boring in comparison.
No, it only sustains 1000 nits for HDR content. For SDR content (including normal desktop usage), it provides 500 nits.[0] You may need to reevaluate your perception of what a 600 nit display would look like.
