To answer your question, there are a number of variables to consider when spacing traffic on approach such as speed, altitude, wind, visibility and pilots being able to see one another is huge in sequencing. As for flying over one another, yes though again there are variables such as how far out on final, is there any wake turbulence separation requirement that has to be met, is the smaller airplane offset from the final until they pass etc. Without the specifics of the exact operation it's all speculation of what occured.
It's a good thing that these flight tracking sites are not what ATC uses!!!
I know little about the two most talked about tracking sites, but can't imagine them being within a minute or two of real time and all that accurate. I am not trashing them, just don't know enough about them. I do know that ADS-B exchange is a very good tracking source full of great information and within a few seconds of being real time based upon traffic flying over the house and sure enough there goes the plane.