Missed parallelism option in plpgsql?

I happened to notice that while writing this in plpgsql
will consider a parallel plan:

    select count(*) into s from tenk1 where ten = x;

writing this will not:

    s := count(*) from tenk1 where ten = x;

Is that intentional?  Seems to me these cases ought to be
treated the same.

The reason for it is that exec_assign_expr's call of
exec_prepare_plan does not specify CURSOR_OPT_PARALLEL_OK.

            regards, tom lane