We already have this problem with the existing claims of being Windows: if we claim to be Windows 8, and behave like Windows 8, we'll still end up causing potential regressions in behavior and forcing blacklists/whitelists. If we start claiming compatibility with a new version of Windows, we'll change our behavior on existing systems. Sometimes that behavior change will improve things, while other times it'll cause regressions. Not with the same granularity, but in practice there are Linux kernel versions claiming to be Windows 8 with one set of bugs, and Linux kernel versions claiming to be Windows 8 with a different set of bugs, one of which may be closer to the behavior of Windows 8. Fixing those bugs may itself cause regressions.

The claim is that by behaving more closely to Windows, we can get away with this, because Windows manages to work on that hardware. However, we're never going to *exactly* match the behavior of Windows, bug-compatibly.