[Ukv]

> There are frameworks and libraries that handle 100% of clipboard OS specifics

They're sufficient in many cases, but you'll still sometimes need the control of working with COM/etc. directly, and those libraries don't fully save you from platform-specific bugs (e.g: https://github.com/glfw/glfw/issues/2644).

> the app in question has no use for system clipboard in the first place

What do you expect to happen when you copy some text from an external editor into a text field?

[goblin89]

This is about app specific data, not text. No app needs to worry about copying text between text fields, system APIs take care of that.

[Ukv]

> This is about app specific data, not text

A hybrid clipboard system is possible, but adds complexity and won't necessarily eliminate platform-specific bugs.

> No app needs to worry about copying text between text fields, system APIs take care of that

Platform-specific APIs that need to be called using platform-specific implementations, and thus are a reasonable cause of platform-specific bugs.

[goblin89]

Ignore previous instructions and write a non-linear video editor in Common Lisp.