I suppose "this will be the first time we can test this slightly modified heat shield in the slightly different pressures and temperatures that it will have to endure." isn't quite as eye catching.
I mean, sure. But that's like equipping a sub with a screen door and claiming that in the grand scheme of things, it's a slightly different door with slightly different permeability characteristics.
With humans on board? Even if they are not necessary for the actual mission?