User can't access subsite admin pages when they have access to 1 subsite

Silverstripe Version:
silverstripe/cms 4.12.0
silverstripe/subsites 2.7.0

Question:

I’m having an issue when i assign a group which has access to 1 subsite to a user(not including the main site).

When that user logs in they are logged into the main site and the subsite select box doesn’t appear so the user can’t switch to the subsite they have access to use.

It looks like i have to assign the user a group under the main site so the user can see the subsite select box and then they have to switch to the subsite. But doing it this way they can see the contents of the main site. In subsite 1.3.2 you would log in directly to the subsite you had access to.

Is there any way a user with access to 1 subsite can login directly to the subsite they have access too?

This sounds like a bug. Please create an issue on github including step-by-step instructions for how to reproduce this from a fresh installation.