If it was a hard link, I suppose my way of thinking about it would make more sense, since all hard links are as valid, pretty much the same. That is, after running

  ln /some/file /other/file

/some/file and /other/file are hard links. So in this case ln is just copying a hard link, while afaik cp would be copying data, making a hard link pointing to the new data. In userspace? That seems to be what's happening here - https://github.com/openbsd/src/blob/master/bin/cp/utils.c

This is made a bit more confusing by the differences in man pages. For GNU ln, it's shown as ln TARGET LINK_NAME, but for OpenBSD, ln source [target]. But the usage is pretty much the same?