On this page https://grapheneos.org/install/cli under the heading "Disabling OEM unlocking" it states:
"During first setup, the final screen will contain a toggle regarding OEM unlocking which is checked by default. This will disable OEM unlocking, which is recommended."
Pixel 4a (legacy extended support) does not have this toggle in the GUI and OEM unlocking remains enabled after device setup. May I suggest the OEM unlocking instructions highlight that not all firmware images contain a toggle to disable OEM unlocking and as a result OEM unlocking must be manually disabled.