Yes really. A pixel is a pixel. This dell monitor has pixels the size of boulders. Apple Pro Display XDR has 4.6m more pixels in a significantly smaller area creating a much denser display.

Denser pixels are worth less because you can't see them; in this case 3x-4x less.

You CAN see then, you CANNOT distinguish them apart without a closer look.

It would be a really ineffective monitor if you couldn't see the pixels.

macOS can specify regions of the screen to be 1x. If I'm using Capture One or Lightroom, my photos are at normal resolution while the UI elements are "retina/2x".

So you can see more detail but you aren't fitting more photos on the screen.

You can configure macOS to scale everything more or less, just like you want it. Same for Windows and Linux. And you keep the crispness of the full pixel resolution for text and images.