"Switch" tenant? Why the need? Please enlighten me to this draconian Microsoft Teams policy!

[Virgil Turner]

Teams > Enable external domains (federation). Domain added to OUR tenant and our customer's tenant. It's frankly UNUSABLE! Here's why: 

• You can only be present in ONE tenant at a time
  • Customers/partners see you as "Unavailable"
  • Audio/video calls they make to you FAIL
  • Chats, messages, mentions appear to succeed, but do NOT reach you at YOUR tenant
• Your customers/partners can only be present in ONE tenant at a time
  • You see customers/partners as "Unavailable"
  • Audio/video calls they make to you FAIL
  • Chats, messages, mentions appear to succeed, but do NOT reach your customer

Here's what Teams user account status looks like when used with federated (external domains) added:

As you can see, you have to MANUALLY "switch" tenant:

The result is that you're OFFLINE in your OWN tenant so that you can be ONLINE in one of the other partner/customer (federated) tenant domains. You will be be able to see chats, messages or mentions from you other teams, and you will be unavailable for audio/video. 

Can someone please enlighten me as to WHY you can't just....chat?

Imagine if this was email, and Microsoft forced every Outlook user to SIGN OFF, then SIGN IN "to the sender's tenant domain" just to read the email and reply!!!!!