It may be the "desired behavior", but it's unfortunately very counter-intuitive and time-consuming to get around. If I have 50 slides, I need to hard code all of them to jump to the previous slide, just in case the user might use the menu to navigate instead of the regular navigation.
If "jump to next slide" follows the numerical order of slides by default, you would expect the "jump to previous slide" to do the opposite.
How about splitting the trigger into two different ones, like "jump to previous slide" and "jump to last-visited slide" ?