He does have a point about grand finalists, at least in recent years. But over those years there are still a bunch of teams with significantly higher or lower win rates than 50%
Just goes to show there's a lot more involved in making (and winning) a Grand Final than just lobbing up in the top 4...the number of people on here who think that just being in the top 4 regularly should guarantee a side bulk premierships (see "Brisbane aren't successful" arguments) is a joke, tbh.
That being said there is no doubt that the sides that have the advantages are the sides consistently making the top 4 and competing for the premiership. But there is more to it than the perceived advantages as well. Melbourne and Brisbane are excellent at identifying and developing juniors, for example, and the advantages they get mean it's much easier for them to keep those juniors. That's the big part Parramatta are missing, we supply a hell of a lot of quality juniors into the NRL system but lack the advantages needed to keep them in the face of big offers from the rest of the competition.
Of course winning things and being a successful side also helps. So does not sacking coaches every two years and having a stable off field hierarchy. So we've got no one to blame but ourselves in many ways.