I guess that might be true for some larger residencies. As someone applying to surgery, the largest group that I've seen is 9 residents/year at any place that I've interviewed, and that often covers up to 5 hospitals. There is simply not enough manpower. Especially if you consider that the largest group in your program (interns including prelims) cannot be alone at any time during call, even with home backup. It would also require more schedule shifting, more months of going back and forth from days to nights to days, and less exposure to the formal teaching. You are probably right in the sense that some of the larger programs could simply have 2 simultaneous night floats, but it wouldn't work out for groups as a whole.
Also, the humane things that have actually started to come out under the 80 hour work week will actually regress under these new rules. It makes golden weekends harder, vacation coverage harder, and it will clearly cause a shift in the number of hours devoted to productive efforts towards scut.
At this point, there is no evidence that there has been a reduction in errors in the post vs. pre-80 hour week period. As we implement more patient safety measures, it will become impossible to tease out what is the result of work hour reforms and what is the result of greater scrutiny within the system. One might say that this benefit is for the residents. However, it is clear that there are a LARGE number of residents, if not the majority, that are opposed to further changes.
With no clear evidence-based reason for the current recs, and no real push from the programs, the residents, or even most patients to change anything yet, I see zero reason to impose a bunch of rules that only serve to make complying with work hour restrictions more difficult. I also wonder if it might be time for some of the surgical specialties to break away from the IOM, which clearly has no understanding of anything that happens in surgical training or practice.