I wouldn't worry about 3 years here or there on the age of a sexagenarian, you know.
The circumstances of his birth were shrouded in mystery. He probably didn't know for certain.
Maybe he was trying to claim an old age pension and needed to make sure that whatever he told the registrar about his age tallied with what he was telling the pensions people.
There could be any number of reasons.
What is far LESS likely is that somebody totally unconnected should have plucked a father's name out of the air and come up with Sydney.
This is often a useful way to test your conclusions in genealogy. The evidence is the evidence. That is a given, and it won't change if you change your hypothesis. So ask yourself "If my hypothesis as to what happened is wrong ... what alternative hypotheses are available?" Then offer those alternative hypotheses up against the evidence, and ask "If this is what happened ... would the evidence look like this, or would it look different?" If the alternative hypothesis would have produced different-looking evidence, then it can be dismissed, because it didn't: it produced the evidence you've actually got!
(That's not to say that once you have dismissed the alternative hypothesis, your original hypothesis must be right: there might be another alternative hypothesis, which you have not considered, which WOULD have produced evidence looking like the evidence you've actually got ... which is why we always say go back and check everything, and recheck it, every time you get some new evidence ... )
