Words "Pascal's mugging" are used when the change of success is extremely, almost infinitely small (but the action is defended by a supposed practically infinite reward). Founding a startup is not Pascal's mugging, even if most startups fail. Buying a lottery ticket is not Pascal's mugging, even if only one ticket in a thousand or in a million wins.

So basically, calling cryonics a Pascal's mugging means that you believe that the changes are much smaller than one in a million. Why would you believe that?

I think we had a survey here a few years ago, and the people who believe in cryonics give it like 15% chance on average; they just think it's worth it. As an analogy, imagine dying from some incurable disease, and then someone offers you a pill that has a 15% chance to save you. You probably would want to spend a non-zero amount of money on such pill.

Yes, cryonics requires some sci-fi levels of technology. However, the world around us already is a sci-fi world from the perspective of someone who lived 100 years ago, and a completely fairy tale from the perspective of someone who lived 200 or 500 years ago. It doesn't seem implausible to assume the same about the future in 100 or more years.

Reviving frozen people does not seem to contradict the science as we know it. It seems mostly like a technological problem, and the future will probably contain better technology.

On the other hand, some things such as the speed of light or the second law of thermodynamics seem like hard limits that even the future people will not be able to overcome. Which suggests that the decomposed bodies in the graves will probably not be revived, even using a sci-fi technology. (Maybe there is a chance that something like time travel will be invented, but that chance seems much smaller that the chance of fixing some frozen cells.)

Not a Pascal's mugging to the best of my knowledge.