It's possible they mean stability in terms of length of support. macOS as an operating system is more "user-stable" if you will, than Windows- i.e. less crashing. But Windows is that way because of the massive legacy interoperability in that codebase. Windows didn't just work because of marketing, it worked because when Microsoft supports something they do it for Enterprise-lengths of time- and with the proper Enterprise tooling ecosystem that Windows has. Ironic that what, probably (some of this is assumption), makes it attractive to Enterprises also probably makes it difficult for them to deliver a OS as solid, to the user, and excluding High Sierra, as macOS.
