Not sure why you were immediately downvoted. This is absolutely correct. Firefox only prioritizes websites over search when what you typed in the omnibar is an exact prefix match for a site.
Take a bookmark for mail.mycompany.com bookmarked as "Email" -- if you type "mai..." it will complete but if you type "emai..." it will search.
Take a bookmark for mail.mycompany.com bookmarked as "Email" -- if you type "mai..." it will complete but if you type "emai..." it will search.