Battery Health of iPhone 12 Pro Max lowering quickly after only about 9 months

I have had this iPhone 12 Pro Max, which I absolutely love (my favorite I’ve ever had) for only about 9 months. But I am already noticing the battery health has degraded to 86% - I have battery charging optimization enabled and this is my 5th iPhone, so I am familiar with best practices for keeping your battery healthy. I charge it fully every night, and it also gets plugged in for a bit when I connect it to my car for the radio & phone calls while driving. But otherwise, I use it as suggested and used to work in a few electronics stores selling and repairing phones, so I know what not to do. I have even started to use Bluetooth lately while in the car to avoid overcharging and making it cord-reliant.

I am curious — is this is covered at all by Apple within a time frame, such as the first year, since it seems faulty to lower at this rate, even with my safeguards in place and optimal usage habits — or is it just considered a maintenance issue, like tires on a car, and there is zero support from Apple with this issue? My other iPhones’ batteries did not degrade this quickly. I still have an iPhone 7S that I use as a backup iPod at this point that still has about 79% health and that is VERY old, since I got it upon release. So I’m concerned that my new iPhone 12 Pro Max is already at 86% no matter what I do. I feel like Apple should cover some aspect of this within the first year. Any information would be appreciated. I couldn’t seem to find a definitive answer anywhere.