Using New Outlook on Windows for personal email, calendar, and contact management
I'm sorry but you should actually know what you are talking about before misrepresenting something. As a real IT professional and not the sorry excuse for the pretend ones on here (I know you aren't representing yourself as such), let me explain to you and anyone who has been misled by your link.
A SHARED INBOX IS NOT a unified inbox - a shared inbox is for a group of people (say the BBC news team) to access the same emails, which will have, for example, the email address of ******@bbc.co.uk. When a member of the news team logs into his/her PC and then opens his/her email, that person will then see, and be able to open, the shared inbox. When someone sends an email to that address it goes into that inbox for all the team to read as long as that person on the team has permissions to 'see' the inbox. As it acts like a separate account this will result in yet another account in your list of multiple accounts.
A unified inbox takes all your emails from every account and presents them in one place, acting like a search (which is why the workarounds for Microsoft's incompetence in this area is to do exactly that - make a search query to act like a unified inbox, which is a shoddy and rubbish solution).
Microsoft NEEDS to get it's useless act together and sort this ASAP