>Futaba, which was the only other imageboard that had guro boards, started cracking down on guro
I don't think this was the case, their nijiura boards were spammed with guro and they created a dedicated 2D guro board on 2002/03/14. It's still there, although always in a vandalized state: https://cgi.2chan.net/o/
There is another (alt) board for 2D guro created on 2010/07/31 too, stuff like jissou go there: https://jun.2chan.net/51/

>except for when he doesnt make backups and tryhard raiders flood the boards and erase years' worth of content.
Not to say it's any more acceptable, but less than 1 year of content was deleted from only one board during that raid