That is correct, the current implementation only checks to see if the document matches the term-window constraints (frequency will be 1 or 0)
This was a design decision to make the calculation faster. Ideally whether to exit early should be configurable depending on whether knowing the frequency is important to the application.
Flagging for 4.1.
Wont make 4.1, bumping to 4.2.
This has been handled as part of 5.0
Fixed in 5.x tree