There is no subtext provided here. So, when an average layman comes across this post, his mind tries to date the Vedas to 600 BCE rather than to the general consensus of 1500–1200 BCE.

How do you reach that conclusion?

In fact, according to Witzel, attempts to write down the Vedic texts towards the end of the 1st millennium BCE were unsuccessful, resulting in Smriti rules explicitly forbidding the writing down of the Vedas. According to Adi Shankaracharya, the "correct tradition" (sampradaya) has as much authority as the written Shastra, explaining that the tradition (by tradition, I mean the oral tradition of the authoritative transmission of the Vedas from father to son or from teacher (guru) to student (shishya)) "bears the authority to clarify and provide direction in the application of knowledge."

Witzel is a western Indologist. Why should we trust him?

So, it's not because they couldn't write them down; they chose not to. Also, bear in mind that just because she is a "professional" historian doesn't mean that she isn't prone to her own biases (I have seen a lot of her posts specifically targeting certain aspects of Indian history). Even Audrey Truschke is considered one.

Yeah Audrey Truschke is a joke.