No markings to anchor cues or a parallax for stereo diff. Try a sphere with regular markings like a soccer ball, or one with side lighting so left and right eye see shadow line parallax.
Ah that’s a distance effect. Depth of field to distance ratio is like 0.004. And imperceptible parallax with human interocular distance of ~60mm. You accidentally nerdsniped me on a current nerd trail 🤣
Interesting diff from telescopes, where distances are so vast, one focal adjustment makes all of (for eg) Jupiter equally sharp. Or even the moon. At least I haven't noticed any depth-of-field effects with even the moon. The ratio of depth to distance for moon is 0.00451653411