Interesting! But in that context, the INTO clause appears to be ignored as there are no values in either B0 or B1, as well as the output being shown on screen. I think that can be further proved by running:
SQL> VARIABLE B0 NUMBER
SQL> SELECT USER_ID INTO :B0 FROM DBA_USERS;
This statement causes TOO_MANY_ROWS exception in PL/SQL, but SQL*Plus silently ignores the INTO clause.
So are you looking for Toad to emulate SQL*Plus and also ignore it?
Disclaimer: Just because I’m learning something new today unfortunately does not mean I get to go home early. [;)]