The one thing I wonder about is whether there might be a benefit to running a lighter casing+insert, vs heavier casing, if balancing rolling resistance with grip and pinch flat protection.
Heavier casings have more rolling resistance, because they are stiffer(harder to deform). So my hypothesis is that the more supple casing, even combined with an insert, would have lower rolling resistance than the thicker casing.
So even though the heavier casing tire was lighter than the combo, I wonder if rolling resistance might still be better.
The other thing of course, is that this depends on the exact casings and inserts compared.
For example, EXO+ with Tannus might be lighter than DD.