"Search in topic subjects" is not the same as what "Search in topic titles" would be. For example, today a poster asked "What is the best touring bike?". I went to search and typed in the words, "best touring bike", and clicked on the "Search in topic subjects" option. The result of the search presented every topic that had the words best, touring, and bikes, whether these words were in the title or in the subject. So that included a whole bunch of topics where someone said something like:
"Next week I'm going touring around the region on my bike. I'm sure I'll have the best time!"
A search option of "Search in topic titles" would only turn up results that had those 3 words in the title.
Here's an example of the search page from another bicycle forum:
Search by Keyword
Option: Search entire posts
Thanks for replying, anyway.