The problematic part is that recipient needs to have MS account to access file. Because when I use sharing approach from OfB - Share with specific people (email) then recipient does not need to have MS account he is asked to fill email and then there is send confirmation password and he has access to file.
Another problem with this Share via Outlook email is that there is no sign about such sharing in Manage access in OfB. No link created, nothing.
For me it seems like this kind Outlook kind of sharing is working strange. Especially when it comes to external sharing.
The question is if that is by design or there is something wrong?
I tried in my tenant and see exactly what you are seeing.
If shared out of OneDrive the sharing works. If shared out via a File Attachment in Outlook, it asks for and requires the recipient to setup a Microsoft account, irrespective of whether Anyone Can Edit or Recipient Can Edit is selected, which is not how it should behave.