There can be risks associated with polishing out scratches on a windscreen if not done correctly or if the scratches are considered too deep to be suitable for polishing out. Polishing too aggressively or using too aggressive a polishing compound can result in dips and hollows in the glass. If this happens and if the polished area is in the driver’s line of sight, the view through the glass could be distorted - similar to wearing someone else’s prescription glasses.
I read somewhere (sorry, can’t remember where) that it’s not recommended polishing out scratches in windscreen glass that are in the driver’s line of sight for the above reasons. However, if the scratches are very light, you might get away with having them polished out - probably best to seek advice from a car glass replacement / repair company.