The idea is that a variable can exist with the same name across account, org and project levels and this mechanism to retrieve variable values do not make explicit reference to the scope, it defines a precedence mechanism instead where the lower level in the hierarchy has the priority.

To provide an example, assume variable "my_variable" is defined at account level with value "A", but then is also created in project X with value "B". If a pipeline in project X retrieves this scopeless variable, it should get "B" but a pipeline in project Y (where this variable has not been defined) should get "A".

Please let me know if further clarification is needed