Yes. Group tracks function as busses - AND they also show up in the mixer as Group Channels.
Consider the channel an “insert” in your bus - actually providing additional flexibility (group processing, level adjustments, further send capability, etc).
Group channels are NOT input channels - and no input can be selected. They are only Group/Busses.
They can be selected as the source for any actual audio input channel . . or other busses . . I mean, Groups (grin).
They can also be selected as the source for an audio export (mixdown). Very nice for pre dubs and stems.
Really quite flexible.
They DO show up in the mixer but as previously stated can be hidden - or used exclusively in a second or third mixer (your “buss” mixer, as it were).
Hugh