You are correct, but a decrease in miles/range, over time (30-40k miles), would indicate a decrease in the battery condition.
Sure, I don’t think anyone is questioning that.
The problem is that all of these similar battery degradation threads are not talking about actual miles driven and are instead making a big assumption that’s based on a range estimate/calculation.
All of this is due to a lack of familiarity with how any EV will behave, which tends to turn into questions/concerns since the natural thing to do is compare it to ICE. The fact of the matter is that comparing an ICE to an EV in terms of energy usage is always going to involve opposite ends of the efficiency spectrum. This difference in efficiency is represented by the fluctuations in range, with the EV experiencing the largest range fluctuations due to its high efficiency and
limited energy density. An ICE does not experience this due to the
high energy density of gasoline/diesel, while also being so inefficient that losing a little energy, similar to what an EV experiences in the winter, isn’t really noticed...
After owning my i3 for 4 years, I’ve come to understand that the 25% range drop during the winter months is nothing to worry about and temporary while outdoor temps are cold enough.. if I compared that result to an ICE, I would definitely think something is wrong.