Not what I said at all.
Let's say as an example, you get 10HP from X mod with the ECU upgrade. The same mod will get you 0-4HP without the ECU upgrade. So you might see gains, but not as much as you would with a tuned ECU. Now that's an example and there are always variables and even cases where certain mods make you lose HP. You just have to be informed so you can make the best decision for your particular situation.
The general consensus has been that our ECU comes set to certain specifications that don't particularly like it when it notices something different, wether it be more fuel, more air, higher revs, etc. So when it starts to notice it, it tries to get it back to the original spec, which basically decreases or nullifies any gains by the mod.