About the Reassemble Step Type
Use a Reassemble step to reassemble previously disassembled components. A Reassemble step does not add another instance of the selected component to a BOM. If you want to add another instance of the component to a BOM, use an Assemble step.
Since you only reassemble components that have been disassembled, these are the only components that are available for this step. Because these components were assembled in a previous step, you do not have to specify a component type.