I don't believe it.
Just tried the picker https://react-spectrum.adobe.com/react-spectrum/Picker.html and within 30 seconds you can find divergences from the browser's behaviour.
The invisible input field behaviour Drew mentions in the article doesn't work. If I hit backspace, my browser doesn't know I'm in an input field and (correctly) navigates me to the previous page.
In Firefox, if I use tab I can select my native <select> and it gets focus styling - not so with Adobe Spectrum React's equivalent control. Once I have focus, I can start typing to select items without opening the dropdown list. Typing whilst I've tabbed on to the React control does nothing. With the native control I can hit space to open up the menu and view the items once I have focus. With the React control, hitting space does nothing.
I also looked at elements like the switch and checkboxes. With native components I can click in the empty space before a form control and be confident that the next <Tab> press I perform will focus the control for me. This behaviour doesn't work with Adobe Spectrum React's equivalent control's - I end up tabbing straight over the components altogether.
> It's such a blanket statement to say "you can't".
It's a blanket statement, sure, but in my experience it's absolutely true and I don't know why it's always frontend JS developers who are arrogant enough to think they can reinvent decades of work on e.g. Gtk in their crappy UI controls library but it's quite tiresome. Spoiler alert: you can't and won't, stop trying.