It's an ambiguous situation.
If you look at the low-level implementation, STORED is not parsed as a
keyword. In other words, the "`sqlite3KeywordCode()`" routine will say
that "STORED" is not a keyword. The SQL language grammar rules used for
generated columns in SQLite looks like this:
~~~~~
ccons ::= GENERATED ALWAYS AS generated.
ccons ::= AS generated.
generated ::= LP expr(E) RP. {sqlite3AddGenerated(pParse,E,0);}
generated ::= LP expr(E) RP ID(TYPE). {sqlite3AddGenerated(pParse,E,&TYPE);}
~~~~~
The optional "VIRTUAL" or "STORED" that occurs after the generated column
definition is parsed as a normal identifier and is passed into the
"`sqlite3AddGenerated()`" routine. Then inside of sqlite3AddGenerated()
(on [lines 1674 to 1682][1]) there is logic to error-out if the identifier
is anything other than "VIRTUAL" or "STORED".
So, from the point of view of SQLite itself, "STORED" is not a keyword.
On the other hand, from the user's perspective, "STORED" does act like
a keyword, even if it is not. So maybe the documentation should be changed
to call it a keyword even though it is not.
I'm not sure...
[1]: https://www.sqlite.org/src/info/912d6ec338311?ln=1674-1682