Staggering news to me. I was born between Apollo 12 and Apollo 13, so my firsthand memories of the program are minimal. But the fact that humans had gone to the moon was a pervasive in my childhood, my earliest books and TV recollections and so on. What a time in human history! And what a pilot! The guy actually took manual control and flew the lunar module till he found a spot where he was confident to land. It boggles my mind, really, what that must have been like.
Actually the lunar module didn't have a manual mode because no human pilot could fly it. What they called "manual" was the pilot bumping the joystick as a computer input, which then added a velocity increment or decrement to its program in an X, Y, Z axis system. During landing the module was also gryo stablized to maintain a level orientation, so the X, Y was controlled by firing the horizontal attitude thrusters instead of tilting or banking.
Semi-automatic mode allowed the pilot to designate a landing point from his window, then the GNC would fly the lunar module close to the designated spot.
Auto mode allowed the lunar module to land at a set of pre-programmed coordinates. No astronaut
ever allowed it to land in auto mode because they were test pilots and test pilots are going to fly the craft to whatever extent they can. So every single time the lunar module approached the pre-determined landing coordinates, the spot was to be "rocky", while a nice clear spot was conveniently nearby, requiring the commander to switch to "manual". Every. single. time.
The programmers and mission planners shouldn't have even bothered with a fully automatic mode because no astronaut was ever going to use it.
There was also an interesting bug in the lunar module approach routines (related to smoothing the flight path, like a spline fit to surface topography) that would cause the computer to merrily fly into the ground (the flight path calculation could interesect the surface if the radar altimeter went across the wrong crater or valley), but the astronauts would make sure that didn't happen, either.