https://github.com/mongodb/mongo/blob/cfb68d2738cea9936e06dcfcb5d89018519970cb/src/mongo/db/admission/execution_control_init.cpp#L30

This will make it easier for header files to add #define + #undef of MONGO_LOGV2_DEFAULT_COMPONENT without causing conflicts.

Example code that follows the convention:
https://github.com/mongodb/mongo/blob/cfb68d2738cea9936e06dcfcb5d89018519970cb/src/mongo/db/admission/ticketholder_manager.cpp#L42