I don't see it so much as crossing a line as wandering into a large gray area. I'm not going to pay a large sum of money for a Mac just so I can try it out. So I thought it would be a sort of "try before you buy" situation to just install MacOS in a VM and play around a bit. If it ever turned out that I decided I liked it and wanted to use it for more than just a few minutes or hours of playing around then I would buy a Mac.
Just because Apple generally doesn't prosecute doesn't mean it's not illegal according to their T&C.
But seriously, installing it in a VM may be more trouble than you think. Part of the prep for installing it on a vanilla PC involves making a bootable USB stick or custom image and then booting from that to do the install; and it's very difficult to make one on anything but a Mac (because the utilities are Mac-based, not because they're trying to stop you). You just can't boot from a Mac image because the modified installation code must be able to identify the hardware configuration of the target machine, much like the Windoze installer operates. It then inserts a custom DSDT into the boot space, which makes the installer think it's running on a Mac. I suppose it's possible, but I wouldn't know where to begin if I didn't have a Mac to create the installer. I'm lazy, so I haven't investigated beyond something that just works for me.