Is there any added advantage on applying more ground stiching vias?
Once you have enough, there's no need for more.

If you're stitching for RF, there's no point in having them closer than lambda/20, and lambda/10 might well be enough.

If you're stitching them for thermal or electrical conductivity, then you need to do the conductivity sums properly. Solder filled vias will be more conductive than open vias.