I think that's true.
I have read the faq from @Anke How to access non-media & media files on Android 11+
and from that I understand that because the files in the shared directory are not created by my app itself (I have put them myself in the shared directory) the app has no read access.
So how can I set READ_MEDIA_IMAGES permission in Mit app inventor?
Is there a extension or other solution?