I was wondering if it uses native controls on each platfrom.

No one does that anymore because the differences between platforms are too large and there is no single platform native controls anyway.

I wonder why this lesson we learnt from desktop GUI development doesn't apply to mobile apps. Seems like the preferred approach there is to use native controls.

The APIs are better.

Come on, what platform has recording studio knobs and sliders as its native controls?

Windows has sliders. I have no idea about MacOS.

Windows does not have those exact sliders that you see in the screenshot. I don't think the available styling options can make them look like that:

https://docs.microsoft.com/en-us/windows/win32/controls/trac...

It's probable doable with custom drawing, but that heavily ties the code to the Windows protocol for custom drawing of controls.