I can see why things like this may be done - the programemr first writes code, then comments it. This may (theoretically) benefit the original programmer in that the code is fresh in his memory, and writing a comment to reflect what it does may "force" him to spot subtle errors. (Of course, same can be said about the traditional "above"-style commenting, but I think the "below"-style makes sense here). I think the "below" style would also benefit a new programmer trying to understand or debug the code - she reads the code, understands (hopefully) it, and then reads the intention - if they dont match, well, there's clearly a problem with the code. How's that for a possible "why?" ?
"Impossible" is just an opinion.