The correlation is in terms of fractions of a year so they add up to an average of plus-or-minus a few month over a lifetime. The three curves don't seem to have a very close relationship to each other though there are some similarities.

I assume that if they are getting a meaningful correlation, it is over a large amount of data. It seems logical that at large scale, date born would correlate with a variety of things in various areas - social class and wealth come to mind.

I think it's a matter of taste whether one says "wow, throw enough data together you find unexpected correlations" or "garbage in, garbage out". A life insurance company could eek out a bit of profit changing its price structure on this data - if it didn't have far more to lose if the use of such tactics became public.

I bet someone can use this to claim astrology has validity too.