The real importance of this is archival. Who knows what would have been burned and shredded to protect the masked brutes.

Trump will anyway throw them under the bus when he's done with them so it's a bit naive to expect their identities would be kept secret forever. And somehow they hoped those masks would do anything else beside terrorize Americans. As far as archival, yes that's a good idea. I'm sure the current admin will attempt to shred everything..