Any time you think the probabilities are anything other than as advertised, follow the following time-honored process:

1. Slap yourself.
2. Do you still think 80% is not 80%? Return to step 1.

Even if the probabilities are NOT as advertised (and no, they ARE just as advertised, but let's just pretend for a moment), it does NO GOOD WHATSOEVER to speculate about it. So, 80% is really 20%. What are you going to do about it?

That leads to players starting to get crazy ideas that there's some kind of ritual they need to perform to reach the listed percentages. Suddenly we've got idiots swearing on their mothers' graves that if you craft while facing west on Iceday during a waxing crescent moon you'll get better results, or other such harebrained nonsense. Keep that crap outta my FFXIV, please!