It is sort of a worthless point, to be honest, that also still has some level of truth haha.
If his argument is that surplus value figures are pulled out of thin air and attached to players based on their prospect list standing, then that's dumb. The figures are historical figures based on past data; that is how much surplus value prospects in those ranges have provided in the recent past.
But it still does bear repeating that figures like that derived from aggregate data will always give you that kind of progression. All it really says is that the people who rank prospects at least have some idea of what they're talking about. Prospects in the 1-10 range, in the aggregate, will be better than prospects in the 11-25 range. What that doesn't mean, though, is that a single prospect ranked 10 differs in any tangible way from a prospect ranked 15 or 20 in a given year. It all averages out over time, which is why the aggregate data gives you the results it does. But in a single instance? It's not really very useful at all in assigning any true value to a single prospect.