Yeah.

If you want to get tin-foily with me I could see there being a conspiracy to keep Beria's actions and the reasons for them sequestered away in the archives out of reach of anyone because revealing the truth would run counter to the prevailing narratives and this info would vindicate Stalin and Beria.

I know this next bit is a line that needs to be dropped on libs more than it does on socialists but it's always worth keeping in mind that propaganda is less often inventing a fictitious narrative than it is in creating a high noise:signal ratio or in curating the narrative by selecting what gets emphasised, at least in the way we're exposed to propaganda in the west today. With that in mind it'd be pretty funny if the reason why Beria's stuff is still sealed is because there's incontrovertible evidence that proves that the Doctor's Plot was real or that the Katyn Massacre was done by the Nazis or that the purges were absolutely a necessity. That sort of thing.

I doubt we're ever going to know the truth about this but when there was a massive airing of grievances against Stalin beginning with the "Secret" Speech and Beria was privy to a whole lot of the excesses of the USSR, if not enacting them directly himself, so it does seem like a glaring inconsistency that they didn't unseal his stuff.

On the other hand it could just be that there's sensitive stuff and state secrets that the USSR and Russia didn't want going public but that's a far less salacious take so it's less fun to speculate about. (Heck, call me a true believer but there's no reason why it couldn't be both...)