That's just more ignorance from a Western indologist who never really studied Hinduism the proper way. The truth is that Upanishads are part of the Vedas. Each Veda is divided into four parts - Samhita, Brahmana, Aranyaka and Upanishad. If you don't know about Hinduism, at least stop repeating the ignorance of the ignorant.Yes, time is often a problem.
Helmuth von Glasenapp, a German indologist and religious scholar, wrote in his book "The five major religions", that the belief of reincarnation cannot be found in the early Vedic scriptures., e.g. Rig Veda or others. This belief of reincarnation can be found earliest in the Upanishads in 800 B.C.