I agree this app works most of the time. If I just use a coin to predict the result, I can get it right 50% of the time. Is 90% prediction hard to achieve? Don’t know. It will depend on how far apart the teams are ranked. If the first ranked team play the second ranked team, I suspect soccer ranking is as good at predicting as my coin.The app does a remarkable job at predicting game outcomes. I looked at one age group for Surf Cup and found that it correctly predicted the outcome of 25/27 games, with only one game that was truly an upset (the other two teams differed by less than 0.5 ranking unit so was basically a toss up). There were several games were the difference in ranking between the two teams' rankings was less than 1 and it correctly predicted the outcome in all but one of those games.
I follow several teams on the app and am familiar with a couple of different age groups and from time to time teams get shuffled and their results intertwined. This could be a glitch in that app (that I believe relies on how teams' names are entered for competitions), especially when team names are similar or shift between seasons or it could be users incorrectly attributing results to the wrong team. If you notice an issue with a particular team and know the team well the app gives you the ability to correct mistakes (add or remove sources). I've found that as the season progresses and new teams have the chance to play the rankings do a really great job and become more accurate with time.
What I do know is a team with that record got grossly misplaced at the top of the ranks. I want to know what happened there. I am not against Soccer Ranking but I don’t like the response from RandomSoccer that the calculation fixes itself after a few iterations. But for $10 a year, maybe my expectation is too high.
It’s also true that this app is not endorsed by any soccer governing body yet we are citing it like the Bible.