Depends on what you use to package. With electron packager (https://github.com/electron-userland/electron-packager) it's really easy and fast to package on a Mac for Windows and Linux. The only real pain for multi-platform packaging is that you need to have a certificate both for Mac and Windows.

It's not hard at all to compile and build a package for Windows on Mac.

On the other hand, want to add an icon to your Windows app from a Mac? Jump down the rabbit hole of installing Wine and other dependencies and watch it spend minutes trying to invoke rc-edit.exe on Mac to make it work.