You can say that. It won't make it true. The point of preloading an angular contact bearing is it keeps the bearing loaded at all points on the rotation. Pitting on a spindle is going to be the result of corrosion, which is going to have a lot more to do with how it was stored than how the cranks were mounted, or contamination, which will attack the whole race.

BTW, I got the adjustment cup out. It wasn't too bad, actually. I used a pair of needle-nose pliers, stuck them into the holes and twisted. With a bit of force, it came right out. The BB was filthy. A surprisingly large heap of dirt poured out, but with a bit of soap and water, it's spinning nicely again. Now... what to do with the stuck quill stem. I'll start another post for that.

Depending on the year of Motobecane, it may be swiss threaded, and not french.

EG, my 1984 Moto is swiss threaded, not sure when they made the change.

bringit to a car garage and ask them to help as they have large sprockets plus power tools ,i had the same problem with my old bike and the job was then done in about 30 sec when i took it to the garage

It won't make it true, but the fact that you are dead wrong about the corrosion suggests you are wrong about that too.

Some forms of corrosion are called pitting, and they even look a little bit like bearing pitting to the untrained eye, but bearing pitting is caused by metal fatigue. The geometry of the situation means the stress is at a peak value somewhat below the surface. That's where the fatigue microcracks start, and they spread upward until a pit of metal crumbles out.

I suppose the bottom of a cone always pits because that's where the contaminants sink to, but the cup doesn't pit as quickly as the cone because the contaminants are floating on oil?

A headset crown race is always preloaded axially due to weight. And it is important to preload the upper races with correct adjustment-but it's not as crucial as the hubs.