Oracle change initialization parameter with "deferred" keyword
I've checked experimentally (Oracle 11.1) that actually ALTER SYSTEM ... DEFERRED SCOPE=SPFILE is allowed, although it seems to me that DEFERRED is ignored in this context. Also SCOPE=BOTH and SCOPE=MEMORY are allowed, obviously. 

What you cannot do (the manual that you quote overlooked it) is ALTER SYSTEM ... DEFERRED on the parameter that has (V$PARAMETER.ISSYS_MODIFIABLE, V$PARAMETER.ISSES_MODIFIABLE) = (IMMEDIATE, FALSE). This results in:

ORA-02096: specified initialization parameter is not modifiable with this option