I think the side menu you circled there only matches with numbers that exist in the call history (not the phonebook or speed dials).
I'm fairly sure that if you delete the call history of the T48G in the picture, it will behave the same as the T48S.
So if for example extension John 100 calls you, then the next time you dial 100 it will show the user on the side menu.
If you delete the history, and dial 100 again, it will be empty again.
You might want to confirm this with Yealink Support if you need further info.