Cross-platform just means more than one platform. Nothing more. There's segments of developer market that don't need Windows support. Those targeting Linux/BSD, Mac desktops + Linux-based backends (i.e. cloud), multiple UNIXen (eg Linux + Solaris), embedded developed on Linux boxes, etc.

I encourage Windows versions of cross-platform apps wherever the app could justify it due to all the developers and tooling on Windows. Yet, non-Windows apps can be cross-platform.