Is this a change in behaviour or a bug?
Please try this.
Open new project
Create some mono audio channels
Create stereo group
Highlight audio channels
Assign audio channels to group (in inspector or mixer) whilst holding Alt (should surely assign all channels?)
Result, only first channel assigns.
I am used to C4, where this action resulted in all highlighted channels being assigned, what has changed and why? Has an error crept in or am I missing something?