Where does RPCS3 store installed updates?

For God of War: Collection [BCUS98229], in the game directory there are three folders:

• PS3_CONTENT
  
• PS3_GAME
  
• PS3_UPDATE
  

...in addition to a "PS3_DISC.SFB" file.

Is the update content always stored in "PS3_UPDATE", meaning that if I wanted to dowgrade I could just move or remove this directory? And is there any need to maintain my own backups of game updates?

PS3_UPDATE contains PS3 firmware, not any game content. It's useless for the game itself.