All you're saying is models are imperfect. That's true. That doesn't mean you need a standard deviation or more than 1 sample.
In this case, the model of 1/36 odds of rolling 2x6 would have to actually be 1/20 (or smaller) to invalidate this test. Do you find it plausible that the bias in 2 die is that high?
In that specific case yes, because there was no dice roll it was just a comic.
In a wider context that single data point is evidence that the detector was tripped or was not tripped. But, unlike a Bayesian the frequentest does not say they then know the actual probability involved and they don't update their priors. Because, to do it correctly you need to pick a P value and a model before doing the test.
Significant: https://xkcd.com/882/ makes a similar mistake by assuming a frequentist would accept that study design before running the tests. Multiple tests require more evidence, though when multiple groups are involved and not all publish you do get this problem.
In this case, the model of 1/36 odds of rolling 2x6 would have to actually be 1/20 (or smaller) to invalidate this test. Do you find it plausible that the bias in 2 die is that high?