No, if the POD was a model of the real TS he used, that'd be 'fair,' I guess. Regardless, they don't have the same saturation content, so you can't say that one is 'better' than the other, since the structure of it changes so much with/without the added gain.
Your logic is flawed in two ways - it implies that we'd set up the amplifiers gain the same way with both tubescreamers, which just isn't true. I would've turned up the amps gain with the OD820 using those settings, which is the other part you've got wrong; do you seriously leave your TS set to the same setting for every tone? Mine changes all the time, depending on how much gain I want from the amp and how much I want from the TS, as well as the difference in response you get from varying the balance between the gain and drive knobs (saturation held constant, you get a different effect with the gain up + drive down vs the gain down + drive up).