Most of the tire info I have seen are from actual, physical rolling resistance tests on drums. There are multiple tests from various sources that show the same trend (even if the precise values vary a bit).
This may not be āreal worldā flat testing since it is on a curved drum, but it is far from ātheoretical modelingā (which implies mathematical and computer analysis). The testing on drums is a relative comparison between the tires with only one variable (the tire itself) changed between the tests.
Even if the actual wattage values are incorrect and not representative of the number we will see on the road, the relative differences between tires are real. The Gators are consistently slower than many other tires to a significant degree. It is real, measurable, and repeatable.