I am aware it doesn't do anything now, but it could do if you accept my suggestion.
Finding threads started by a member is daunting task:
Click Search
Enter member's username
Click Search
Click member's icon to visit his profile
Click Find
Click Find all threads
Beside that, it is not possible to do any kind of advanced search with it. It will just display all possible threads, i.e. cannot limit them by forum, date, order, etc.
Also grouping results by thread is not the same thing as finding threads started by a member.
Right. But it is working as designed at the moment so if you have suggestions for change they should be made in the suggestions forum, not the bug reports forum.
In your original example, you are not searching for any keywords therefore "Search titles only" shouldn't have any effect. You can't search for words that appear in titles if you don't enter any words...