That complicates a lot of things. You are basically making a new product, with all the complications (and costs) associated with it. And where do you stop? What decides if it has impact or not? If I change the brand of a capacitor do I need a new model? Of course not. If I change the model of a switching controller? Well, still shouldn't change anything, but let's obvious. If I change another integrated circuit (i.e. a small SPI flash used to hold the firmware, or a i2c temperature sensor, or a supporting microcontroller)? Likely doesn't impact that much.