Email recipient list does not contain all queue member's email addresses

The behavior of the email recipient list is controlled by the Case Assigned Template setting in Support Settings and is working as designed.

In Salesforce Classic:
Setup > Customize > Cases > Support Settings

In Lightning Experience:
Setup > Feature Settings > Service > Support Settings

For example: Create a queue and add multiple members. Select the "Send Email to Queue Members" checkbox for the queue. Go to a Case and assign the case to the queue and select the "Send Notification Email" checkbox.  

If Case Assigned Template = --None--, then all users receive an email with other recipient's email addresses
If Case Assigned Template = Something other than --None--, all users receive email with their own email address but no other email addresses.

Note:

When sending an email alert to members of a queue using the default email template in Case Support Settings, all members of the queue will receive an email with the other member's email addresses included.