Lord Spandex Masher - They weren't 400 feet high. They were 400 feet above a 3 degree profile. There's a difference.
You are correct. In the sense that they are not high until they cross their stabilized approach gate. Whatever that is for Asiana.
Can we agree that the goal is to be stabilized on glide path or glideslope, at a specific altitude ? In this case, they must lose 400 feet in addition to continuing the descent towards the runway. That requires a rate of descent that is higher than normally required on a 3 degree glide path. Five miles from the end of the runway.
A normal rate of descent at Vapp is approximately 800 FPM. Traveling at over 2 miles per minute, 5 miles from the runway. If you descend at a safe rate of descent of 1000 FPM, it takes 2 minutes to lose the extra 400 feet. At this point you are now 1 mile from the end of the runway. Hopefully at 500 feet. All doable if well managed, fully configured and on speed when you cross the bridge. Even I can do it, on numerous occasions. It certainly requires greater that 1000 FPM ROD if you are still configuring and slowing.
What was their rate of descent ? Were they still slowing and configuring when they crossed the bridge 400 feet above a 3 degree glide slope ?