not only is the data they have unlikely to worth the amount they're asking (or they would have made their demands back in Feb when they acquired it), it's quite certainly not going to make Reddit do anything to change their position. At worst, I would suspect, the data contains some mildly interesting internal Reddit gossip and confirmation about what everyone has suspected for over a decade regarding exactly what telemetry Reddit collects on its users. I doubt Reddit would even be embarrassed by it-- nothing seems to embarrass the shameless.
The only potential value I can see in this action is to further scare off potential investors and to further delay the IPO. Maybe.