What did they say?
I have used the magic keyboard on a iPad Pro and you can not use it as a tablet as the keyboard can not be folded back, a lot of tech youtubers say that as well if you watch the videos they will show you.
The iPad Air 4 and iPad Pro 11 inch use the same magic keyboard so it hasn't been changed designed wise.
I have an iPad Air 3, I just use a simple case which I can use as a stand, covers all the sides and back, I do use a Smart Keyboard, but the iPad Air 3 smart keyboard does not cover the back, so I bought a specially designed case which covers the back and sides and can be used with a smart keyboard it was really cheap.
I have used the magic keyboard in the apple store and my friend has one and as I said you can see on the videos on YouTube it can't be folded back. it's either folded down as a case or being used as a keyboard there is no in between
Logitech do cases/keyboard which might offer the support you want, they are really good and apple sells Logitech stuff, so might be worth checking out, but make sure it is compatible with the air 4, it's not all ways the clearest on the Logitech website.
Hope that helps