@for clarity

The /pANinIya is not a book for the student, it is a bunch of notes for the teacher, that the teacher is supposed to memorize AFTER knowing he meaning of every sUtra. That is why the meaning of a sUtra is not supposed to be inmediately evident to the person that hears the sUtra for the first time.

/pANini doesn't give a damn about that. Sutras are supposed to be precise, consistent, and to be organized in such a way that the whole grammar is ASHAP. That is why a sUtra will be worded as "replace /ru before /sup'", when wording it as "but replace only /ru before /sup'" would have been much clearer — just to save the space that the /tu and the /eva would have taken. The clearer "supituroreva सुपितुरोरेव" would have been too verbose, rossupi is shorter, and suffices.

So, whenever /pANini uses any expression that might have easily been shortened or erased, the commentators are puzzled and try to find a good excuse to explain away why /pANini didn't do so.

If they can't find any good one, then /spaSTArtham, literally "for clarity", will do. You may, if you want, translate that as "it's clearly redundant, /pANini might as well have done without it".