So, that's largely a myth that's been propagated by Apple fanboys. The reality is that OS X (and previous iterations of the Mac OS as well) are just as vulnerable as Windows, but there aren't as many examples of those vulnerabilities being utilized simply because less desirable targets operate on MacOS. I will grant though, that the Unix backbone of OS X is definitely a benefit, though most people will go through their entire computer-using lives without using the terminal in the slightest. Another factor of security in OS X (which has, to a degree been copied by Windows iterations) is the use of superuser access, where traditionally in Windows people would be signed in with an administrator account that could do all manner of things. *Nix-based OSes (Linux in various flavors, Unix, and derivatives) will have you signed in as a standard user, and in order to execute privileged actions you need to input an administrator password, which can help protect the user from themselves. Windows has introduced this in the form of User Account Control, however the problem here is that most users see it as just another step, and will turn it off without knowing the implications.
I won't turn this into a this-versus-that discussion and don't really want to go down that path, but it's the same as the idea that MacOS is better for graphic design work -- this stopped being a thing with the end of using Apple's PowerPC architecture, since they started using x86 the playing field was even between the two. I don't have knowledge regarding the M1 chips, but it was a commonly-parroted falsehood that hasn't been accurate for a long time now.
