No one is denying progress in theological understanding within the church. The difference is that Augustinian and later developments were squarely based on the Bible.
Modern dispensationalists pulled their definition out of thin air, e.g., "A dispensation is a period of time during which man is tested in respect to his obedience to some specific revelation of the will of God" per CI Scofield.
Modern dispensationalists, at least the ones hanging around here, have tried to make some identification between the early church fathers and modern dispensationalists based on the simple fact that they both used the same word.
That has been demonstrated to be patently untrue.
Hardly.
Dispensation has been shown to be a word that comes from the stewardship/administration of an enterprise or other area of responsibility.
That's what it means biblically. That's how it's used in each instance.