Let's check it out:

Baseline DisplayHDR 400

• True 8-bit image quality
• Global dimming – improves dynamic contrast ratio
• Peak luminance of 400 cd/m2
• 100% sRGB coverage NOT needed, 95% only

DisplayHDR 600

• Peak luminance of 600 cd/m2
• Full-screen flash requirement
• Local dimming
• 90% of DCI-P3 gamut. Why 90%, what 90% means actually? As each monitor can be different such way.
• Internal 10-bit image processing, but still cheap 8bit panels.

DisplayHDR 1000

• Peak luminance of 1000 cd/m2, can't retain such brightness for long(!)
• Local dimming
• 90% of DCI-P3 gamut (again 90%!)
• Internal 10-bit image processing, but still cheap 8bit panels.

Even best displays won't be able to retain even 1000 nits, except for flash. It makes backlight cheaper, as well as stupid TV energy saving rules can live longer happy.

Contrast requirements are very lazy, as making even IPS monitor with 1:1000-1500 is not hard, it is ordinal numbers now. Actually whole limits are made with IPS consideration, as for VA and OLED panels parameters can be much higher.

They also allowed to keep cheap 8bit panels, but now call them "10-bit" by adding dither.

In reality minimum must be 5000 nit peak, 2500 nit retain, 14 bit processing, 10-12 bit native panels, 1:4000 minimum contrast. 100% DCI-P3 coverage. But leading firms won't like it, as profits will be much smaller such way.

For sure we will see such standards, 2 years from now, as they ask you to change your TV and monitor again.