If they're calling a brain their original processor, these robots could be a result of successful transhumanism rather than conventional robots, ie, they could be humans that have made themselves into robots, rather than robots built for some specific purpose. In that case, they might create child robots and grow them over time to reproduce, just because they find that mode of reproduction familiar and wish to continue it.
Could just be a compact model, the big one could just be stupidly pointing out the obvious to a far more advanced compact model that's just given a lecture on the history of robotic processors.
The compact advanced model might just be about to say "Very good, I'm glad you were listening".
I like to imagine that the childbots are made in the image of the parentbots, and the childbots eventually are tasked with picking out preferred larger parts as a growing rite.
From the moment I understood the weakness of my flesh, it disgusted me. I craved the strength and certainty of steel. I aspired to the purity of the blessed Machine.
Your kind cling to your flesh, as if it will not decay and fail you. One day, the crude biomass that you call a temple will wither, and you will beg my kind to save you.
But I am already saved. For the Machine is immortal.