I have a hypothesis on why people think a 75% victory chance is unlosable. It is because people are just not internalizing it as a 'win percentage' but simply as a stat.
Actually, "people" are rigth with their assumption, and Sid proves to have not understood the mechanics of his own series.
Another simple example.
You have party A having 2.000 riflemen and party B having 1.000 riflemen.
Each individual rifleman has a chance of 50% hitting his target.
Which in reality would mean that with the first volley, party B would have lost ALL of their riflemen, thus losing the battle.
In Civ4, the calculation is different:
A/(A+B) = 2.000/3.000 = 0,66666 (for the first volley).
So, with a chance of mere 66%, party A will have a hit, reducing party B's health by 5 or 6 of 20 points, leaving them with at least 14 health points.
And so on.
The result is, in Civ4 party B has really a decent chance not only to survive, but actually to win the battle.
This is just completey unrealistic and not plausible. In realitiy, the 2.000 riflemen *WILL* win the battle. It may be that they have to take more then the expected 500 losses, but finally they *WILL* win.
In Civ4, they have good chances to lose.
The way in which combats were resolved in Civ4 was just a mess, and Mr. Meier defending this way just proves that he has not much understanding of what his games are doing.
Actually, they have been based on distorted combat calculations since long.
tl;dr: Yes, Sid Meier has created Civ1. Yes, his name has been attached to any Civ game since then.
No, he doesn't understand the genre nor does he understand the way "his" games are working anymore.
I wouldn't put too much hope into Sid Meier anymore. Even less, since he is promoting Civ Facebook so much.