1. The theory fixes the period of Vedas as 1000 BC which is not right. Bhudha himself is 600 BC. Before him there is a big line - Krishna, Rama, and Various rishis and Vedas.
2. The hypothesis quoted says vedas were later to Indus. But Indus itself is vedic.
3. The emerging theories relate - Tamil as a spoken language and Vedas as a divine revelation with focus on pronounciation than meaning.
4. Hence Vedas require much practise.
5. Hence a separate spoken language should have existed and that is Tamil.
6. Sanskrit originated from the vedic language.
No Aryan or Dravidans related to race. May be related to place.
Some state this straight away and some beat around the bush.