I don't remember every detail of that part of the programme, but I do remember thinking 'whoa..' when Rupert found the entry just like that, as Tommy Cooper might have said. Yes, it came up on IGI but there was nothing to confirm it was the correct one, could have been co-incidence.
My assumption last night was that the research had been done in detail prior to the programme, the programme makers therefore knew it was the correct record and, as discussed at length on here in other threads, they just filmed him finding the 'quick win' because they are making a TV show, not a tutorial on the pitfalls of instant answers in genealogy.
That was my feeling last night, and probably still is, though I would be interested to hear if anything further develops