Using real Boolean type in SAP ABAP

This way is called as a Predictive Method call. This will work if the initial value is false and false is the initial value. You can refer to below link to know about Predictive method call and also to see examples:

https://help.sap.com/doc/abapdocu_750_index_htm/7.50/en-US/abenpredicative_method_calls.htm