right, but this is a problem in any modern precision machining, and it has been (mostly) conquered to a degree that we can produce very precise things in an almost entirely automated fashion.
>If material is missing somewhere, you could have the machine go back and add it
laser sintering is easier to audit than a normal fdm style print in a lot of ways if you care to take the time to do it. The process can be paused fairly easy with the right machine and right environment, the product can be weighed mid-process, it can have all sorts of vision and laser metrology done to the product midway through production; whatever -- and the mid print failure rate is astronomically lower than extrusion based methods.
it doesn't seem that unbelievable to me.
The most common form for metal precision production is powder bed fusion
You deposit a whole layer of powder and a laser melts the desired parts
The layers are really thin, so manually inspecting them would slow down the printing process drastically. Then, ultimately, what even can you do if there's a defect? The layer has been laid already. If material is missing somewhere, you could have the machine go back and add it, but if there's excess material somewhere, or it's in a form that the machine can't fix, there's not a lot to be done, particularly in applications like rocketry, where your structural strength tolerance are very tight.