I’d say BSD (esp Net and Open, as mentioned above), just don’t run as many processes, by design. BSDs are *nix, like Linux, but with their own traditions. If you, familiar with Linux, sat down at a NetBSD box, you’d be able to easily get around like a little girl[0]. You wouldn’t find systemd, though, you’d see a “wheel” group, your login shell might not be bash. The BSDs just decorate their houses differently than Linux[1].
I'd say it depends on the Linux distribution. Things like Ubuntu would be much like mentioned [1], packing just about everything¹, while on something like openwrt you would probably recognize or easily find out the function of all userspace processes - I counted 13 on my router.
It doesn't help that linux (kernel and userspaces) tends to resemble chaotic patchwork more¹ than a reasonably designed system.
¹ exaggeration
Of course you are correct; “Linux” is a big landscape, and descriptions of instances run the gamut (eg: OpenWRT vs Ubuntu). When I was writing above I had (eg) Red Hat or Ubuntu in mind.
I had always assumed (probably ignorantly) that BSD basically runs all of the same or similar processes to a similarly featured Linux distro.