I've bolded the error for you.

Determining value requires looking at more than one single redemption.

AC imposes significant fuel surcharges (or, "scamcharges" as they call them on the AC forum) on most award redemptions. While there are a few instances when an award will cost less on AC, most of the time the AC redemption will be more costly.

There is also the issue of elite status. If you credit your UA flying to AC, you're not going to earn status on UA. So there go virtually all of the FF perks (which, despite the negativity on this forum, are still substantial).

Finally, as already noted, AC is rather stingy with their mileage credit on discount fares.

Go spend some time on the AC forum, and you will see how AC's frequent flyers feel about AP these days.