Will that give an exact location or general?
Find My Mac only works on Macs connected via WiFi. It does not work for computers that are connected via Ethernet and have WiFi turned off.
That support article is about iCloud in general, not the Find My Mac specific functionality.
Yes, wired Ethernet will provide access to iCloud, but not Find My Mac (unless WiFi is also turned on).
Same thing for using Apple Maps. You can use it fine on wired Ethernet, however you won't be able to locate yourself on Apple Maps unless you turn on WiFi.
Try it yourself.
Why would it only work for wifi? That makes less than no sense to me.