I don't see that being the case, no. A physics engine is a physics engine. When you give an entity properties of a human body, the engine should treat it as such. It doesn't matter if there are 2 bodies or 200, it should be more or less the same thing difficulty wise (without considering hardware power of course). I don't think FIFA having less human to human interaction but the same amount of bodies on the field makes it any easier to produce. Also keep in mind Madden 360 has 2 years under its belt now.
As someone stated above, however, EA can't even get 60fps with Madden as it is now with an animation system pre-dating the year 2000. I think there is a very real possibility they simply are not skilled enough to get real physics in an NFL game optimized enough to run smooth, or maybe the 360 just isn't as powerful as it is made out to be. Physics processing is NOT a strong point of these "next gen" consoles, which could be a major flaw given that real time physics is clearly the next big leap in gaming of all genres.
Programmers program what they are told to program. They are grunt workers. Producers are in bed with upper management, who see this as a dollar business, which it is. Some development houses - idSoftware, Blizzard, etc - are far less rigid in this regard but that's because they're selling fantasy usually, so they have to think outside the box. Couple that with the fact they typically get more than 12 months to make a game with a set deadline. This basically forces EA to focus on features they feel will best sell the next version - gimmicks. This is why stuff like double team blocks, gang tackling, extensive gameplanning etc never seems to make the cut, because each year they need front cover features to sell the game to the market they have created.
Programmers are probably just like us. They'd probably love to see the stuff we want, but that's not their decision to make. My stance is, EA should hire enough programmers so that they can cover both bases, particularly considering how much money Madden makes them. But that's not going to happen without competition - as I said, bare minimal = maximum profit, if you define 'minimal' as 'the least amount needed to be done to sell', which isn't very much for the typical Madden buyer.