Apple Studio Display - disappointed with depth of blacks

That is to be expected, unfortunately the Apple Studio Display doesn't have the XDR technology as the MacBook Pro. You'll need the Apple Pro Display XDR to get similar levels of blacks.

If you check the Tech Specs, you'll see the following:

• MacBook Pro has an Liquid Retina XDR display, this means 600 nits in SDR, 1000 nits in HDR sustained, with 1600 nits peak in HDR
• The Pro Display XDR, come close to the MacBook Pro Display with 500 nits in SDR, 1000 nits in HDR sustained and 1600 nit peak HRD. You'll notice that in SDR it's only 500 nits, when compared to 600 nits from the MacBook Pro. Unfortunately this also doesn't support ProMotion, meaning no 120hz refresh rate, it's limited to 60hz.
• The Studio Display, only supports 600 nits SDR, it doesn't support HDR, also no ProMotion

Conclusion, the  Studio display doesn't have mini-Led, meaning it can't turn off pixels, so it can't produce those deep blacks, that's why you see that discrepancy.

The big version of iPad Pro is the only other product that has this mini led technology, basically the Liquid Retina Display XDR, but it's not available on the smaller version. iPhones and  Watches use OLED technology, meaning that each individual pixels can be turned off.

+1 to both of you for a high-quality 1600 nits XDR brain food discussion! Don’t see that too often around here…

Nothing to add except to state the obvious: you had 10 days for Apple to take care of buyer’s remorse, no-questions-full-refund-return. Hopefully that’s what you did!

While the Studio Display is not HDR something is not correct here. My Studio Display has very good black reproductions. As matter of fact it has much better depth of black than my other two displays which are LG 5k and 27" iMac. I see little difference between the Studio display and my MBA. I would go back to your Apple store and check their display. Perhaps you may have some issue with yours. Also I have no bleeding at any location on my display which yours appears to have.