sql-update: WHERE CURRENT OF cursor

Just to make sure I understand. In the 7.2 documentation,
sql-update.html, at the bottom it says:

Compatibility

SQL92

SQL92 defines a different syntax for the positioned UPDATE statement:

UPDATE table SET column = expression [, ...]
WHERE CURRENT OF cursor

where cursor identifies an open cursor.

Does this mean that one can not do an update based upon a cursor's
current position??
If so that kind of limits the uses of a cursor, one has to not only do a
SELECT but then
an UPDATE where the whole table is once again scanned???

Also, I tried to use a column name in a SELECT ... FOR UPDATE
column_name,
but I could not, it wanted the table_name. This is an incompatiblity
also but does not
appear in the documentation.

Richard