Just to add to this discussion: If OpenCore is configured with RequestBootVarRouting, anything blessed within an OC-booted system will be rerouted to boot through OpenCore, so it actually becomes difficult to leave OC without taking drastic measures like pulling out the disk where OC is installed or deleting the OC files. In fact, even resetting the NVRAM doesn't guarantee that OC won't start. So to properly leave OC:
1) Use Startup Disk to select Mojave.
2) Turn off RequestBootVarRouting.
3) Reboot (so that the new setting can take effect).
4) Use Startup Disk to select Mojave again (this time the selection is not rerouted through OC).
5) Reboot. Mojave will start outside of OC.
6) Turn on RequestBootVarRouting. OC is now ready for its next blessing.
1) Use Startup Disk to select Mojave.
2) Turn off RequestBootVarRouting.
3) Reboot (so that the new setting can take effect).
4) Use Startup Disk to select Mojave again (this time the selection is not rerouted through OC).
5) Reboot. Mojave will start outside of OC.
6) Turn on RequestBootVarRouting. OC is now ready for its next blessing.