OptionalWithoutEvaluate as though the system user did NOT hold this role.
For the guard on removing a role from the account: taking a role away removes its rules
from the aggregate, which can strip the last Allow just as surely as editing one. Both the
field rules and the entity-level ceiling are re-evaluated without it, so a removal that also
costs the account its entity-level read is correctly permitted — it is then denied one level
up, and field rules decide nothing.
Narrowing for FindSystemUserFieldAccessViolations.