>> Can you give examples of that?

> There is a link to the Open firmware site on the page that he referenced
> that specifically mentions this technique.

I guess you mean this statement:

"In most cases, the Open Firmware implementations provided on this site rely on an additional low-level firmware for hardware initialization, such as coreboot or U-Boot."
https://www.openbios.org/Welcome_to_OpenBIOS

The OpenFirmware implementations mentioned on the left are Open Firmware, SmartFirmware, OpenBOOT, OpenBIOS and SLOF. For SmartFirmware, the statement is obviously untrue, as can be seen by the Pegasos and the Efika 5200B. And also SLOF doesn‘t rely on another low-level firmware.