'scholar' desperately needs it to be 'impossible' for a contingent of Jews to have prepared for a journey from Babylon to Judea in just a couple of months. Of course, it is entirely possible that teams of people could have made the necessary preparations, and many sources agree that 538 BCE is the correct year. But 'scholar' needs it to be impossible even though it is supposedly possible for God to accomplish anything.
JWs believe the obviously mythological story of Moses and the 'exodus'. In that story, Moses was 80 when he spoke to the conveniently unnamed pharaoh, and after 40 years in the wilderness, he was 120, so he was still 80 when they supposedly left Egypt in Abib (March/April) of, according to JWs, 1513BCE (according to Bible chronology this would actually be 1445BCE, though it doesn't actually depict a historical event).
Even after Moses had initially lied to the anonymous pharaoh by asking to just go on a three day trip (Exodus 5:3), the Israelites (purportedly millions of them according to Insight, volume 1, page 778) had still not made any travel preparations because they hadn't listened to Moses at all (Exodus 6:9, 12). The series of events in chapters 7 through 11 explicitly cover only a few days, repeatedly referring to "tomorrow", and even part way through the plagues, Moses was still telling the lie that it was just for a 3-day trip (Exodus 8:27). So the Israelites apparently required very little time indeed to prepare for their journey from Egypt to 'the promised land' which was then supposedly interrupted by 40 years in the 'wilderness'.
So, even though it is actually practically possible for the Jews to have organised a journey from Babylon to Jerusalem in a few months, in view of JW superstitions, it is especially preposterous that 'scholar' believes it is 'impossible'.