Why wouldn't it continue at 9 degrees?
Because the "inertial mode" is intended to jump in temporarily during a 3° approach with a poor ILS signal lost temporarily. There is no 9° approach for a 747, which would be far beyond the "steep approach" some significantly smaller aircraft are certified for.
The real question is: How can you cross two markers (Outer and middle) without doing an altitude check? The according numbers are on the approach chart, so no math included. Dead simple crosscheck, but not done.
If you do no crosschecks, you are not allowed to do any mistake or darwin gets you.