The only thing I can say is this.

When it says you have a 90% chance of success that means for that attempt only. SO the computer randomly picks a number between 1 and 100 and if its 90 or less you succeed.

If you fail and try again
The exact same process happens.
There is no adjustment to it for previous successes of failures.

SO this does give the appearance that the success rates are over stated even though they are not.

However I hate that it is done this way.

People get upset because they fail something at 90%, so a logical expectation is the next time it will succeed. But that is not the case because the success/failure of the next time does not take into account any previous attempts. SO it does not seem like the percentages are correct. It was the same way on evony.
Do not expect them to change it.