For me, the similarity is not primarily from the looks but from:
- The opinionated "GNOME"- or "Apple"-Way to do things
- The focus on using workspaces (Although Apple forces you more to use them than GNOME does)
- The focus on design before features (I feel like this is more of a GNOME thing but it aligns with the philosophy Apple tries to exhibit about itself)
Then alongside that, I also get that MacOS vibes from more minor things, like GTK or Apple AppKit (?) providing one unified design language across almost all apps, as well as the touchpad gestures.