Maybe they choose it because it's the lowest risk product?
When Apple was just buying parts from Intel, a lot of those parts had already been mass produced and tested in other products from other companies so Apple was reasonably sure that failure rates were sufficiently low.
Now that Apple makes their own CPUs, they don't have a good way of knowing that no defects exist that cause 1% to fail after a year or something. So they pick a product line where such a failure would be easiest to deal with. As a cheaper product, they could just give a replacement. Might be fairly easy to repair. And full refunds might not be so expensive.
IDK, I'm just making stuff up.