It mixes them because it's a small educational example, no one stops you from following MVC practices if you want.

Most of the Red GUI examples I know of are "programming in the small", like CRUD interfaces, games, and various interactive environments. [1, 2]

The graphical engine relies on OS widgets internally right now, which are resource-heavy and don't scale well (at least on Win32 backend each widget is just that, a window); in the future, more lightweight graphical objects (aka GOBs) will be introduced for use-cases like spreadsheets and data-intensive apps, there's already a PoC for that. [3]

For evaluation and benchmarking, I recommend to check out 7GUIs project [4] and add Keera Hails entries to it; here [5] is Red implementation, for comparison. Some tasks in it directly address MVC separation of concerns.

[1]: https://github.com/red/code

[2]: https://github.com/red/red/wiki/%5BLINKS%5D-Projects-showcas...

[3]: https://github.com/qtxie/red/tree/GOB

[4]: https://eugenkiss.github.io/7guis/

[5]: https://github.com/9214/7guis-red