There is no way to prove or disprove such claims. You have mentioned the Sarasvati hymn in Rig Veda VI.61. There is another mention of Sarasvati in Book 7.
This stream Sarasvati with fostering current comes forth, our sure
defence, our fort of iron, as on a car, the flood flows on, surpassing
in majesty and might all other waters;
Rig Veda VII.95.1