Letter to Gmail Inbox team: Strange thing — Is it bug or feature?

We all already know that Gmail team trying to invent our classical view of mail. And one of this brand-new product is Inbox. I was one of the first testers and I noticed one strange thing. Does it bug or feature?

Let’s see. In my android phone I have two gmail accounts, mine and my girlfriend’s. When I received invitation from my friend, I downloaded app from Google Play and signed in by mine own account m.****n@gmail.com. But also I noticed that I can switch between accounts: mine and my girlfriend’s. You can see it on screenshot below.

But one main thing is my girlfriend does not have Invite, why she can access to inbox? I also checked it on third phone.

When I tried to install and login in Inbox app by girlfriend’s gmail login was successful. Here is screenshot from her phone.

Then I tried to add new gmail accounts on my phone, I add my test account m.s*****test@gmail.com. I found new checbox in sync settings: sync Inbox.

And login was successful.

I checked it on third phone, and it was successful too. If I can add unlimited emails, does it mean that I have unlimited invites?

Dear Gmail team, Is this bug or feature? Looking forward for your soonest reply.

Best regards, Marat Shaken

m [dot] shaken [at] gmail [dot] com

P.S. And here is the answer from Security team of Inbox:
“Hey, Thanks for your email, but I’ve confirmed this is working as intended. It would be an extremely poor experience if you couldn’t use Inbox on all the accounts on your phone.
cheers, adam”