This is a well-known and popularized myth about the ancient scriptures which plays on patriotic feeling by claiming "uniqueness" and advancement in ancient India. It is manifestly not true or based in fact that any of these technologies existed at the time - there's simply too many holes (why didn't any other culture reproduce these fantastic feats or obtain access to these? where is the archaeological record? why did no other text from the time corroborate this story?), and the best "evidence" the scriptures even talk about this are generous translations that don't accord with the actual historical or linguistic data.

This sort of myth is yet another distortion of the past in favour of a narrative enshrining pre-modern India as superior that has taken ahold of my country. Only in India will people claim Valmiki's is the only valid version of the Ramayana (there are hundreds of versions of the Ramayana, some told as far as Thailand, of which Valmiki's is just one - see A. K. Ramanujam's "Three Hundred Ramayanas"); make homeopathy derived from Ayurveda a nationally accredited field of medicine despite overwhelming clinical evidence it is no better than a placebo; and claim the Vedas predicted the inventions we take for granted today. It is misplaced reverence untempered by an awareness of how to interpret historical documents, and all it serves is to blind people to facts and common sense.