All
Multics documentation and books prior to 1974 or so are pretty much wrong. Multics was actually written in
PL/1,
EPL was used for only the early systems, while waiting for the full
PL/1 compiler.
When they moved from the GE 645 (software rings, etc.) to the GE 6185 (hardware rings, etc.) they went to 8 rings. By the end of Multics releases, the OS was quite mature, supported databases, and pretty much erverything that UNIX would like to have (Multics didn't have pipes, though).
About 1972 or so, the General Electric division that built GECOS and Multics computers was putchased by Honeywell. The GECOS operating system was renamed GCOS, and they continued to build hardware in Phoenix, Arizona and write software there and in Cambrige, Mass.