It reliably kept within the correct range when I search within and search forward. Going backwards, it stopped at the right spot too.
There is a small side effect. Having performed an advanced search I then modified the search term in the search box in the tool bar. The new search fails to find the search term. The error dialog displayed suggests that it is using the conditions provided by the advanced search. However, that is misleading. The search term should have been found within the advanced search criteria.
Interesting. One little tricky thing that might be tripping you up is that, if you select one of the new scope options, and then perform a search, and then modify the search term, the search for the new term will be performed with the previously selected scope, but using the currently selected Note. So, for example, if you had previously selected within, and then searched (moving the current note selection), and then changed the search term, you would no longer be searching within the original scope.