It's not the case that randomly-generated weights will not have biases. The point is that if you generate weights randomly the computer will still have biases, you just don't know what they will be.

Yes, the difference between bias and preconception is exactly what, or are you being bias?

Seriously, lookup the meaning of the terms and see if what they mean are what you believe them to mean.

A preconception is an idea. A bias is much more general. If you're putting in a table, and you don't make it quite flat, you have biased the table, but you have not instilled preconceptions in the table.