The multisession standard actually afforded the possibility of CD-PROM; a hybrid disc with a pressed read-only session followed by a writable section. It was only used for Kodak Picture CD (not the same as Photo CD) to hold software in the pressed session. It also apparently standardized a magneto-optical hybrid that never made it to market.

It was also used by Ricoh EncryptEase - CD-Rs with encrypted backup software in an initial pressed track. https://www.youtube.com/watch?v=_5ucImqdKbY

Hmm, it could work then if they’ve pressed most of the game data first and then recorded the encrypted part for each disk. But I guess the tooling for such setup would still be too expensive.