Battery Health Unchanged during last year of AppleCare+ Coverage

I have a MacBook Pro M1 (2020) since December 2020 and I got it with AppleCare+ for 3 years of support. I have used it as usual for what's almost 3 years now and I eventually check my Battery Health, as I do with all my other Apple devices.

During the first 2 years I noticed a normal decline of the battery as you'd expect, specially as I use the battery a lot, instead of keeping it powered.

At the beginning of this year my Battery Health was at 84%. I have a screenshot of it as I was going to sell my MacBook to a friend and I sent this info over to him. I ended up deciding to keep my MacBook.

In the last couple of weeks/months, I noticed that my battery has consistently drained quicker than usual and I can't get a full day of use as I used to a couple of months ago.

But even though the battery has been significantly worse, my Battery Health is still at 84% and it hasn't changed for almost a year now.

What's most interesting is that I am getting close to the end of my AppleCare+ coverage, which would allow me to get a free battery replacement if it ever dropped below 80%.

Now, before assuming that Apple is freezing my Battery Health to avoid a free repair, I wanted to check if anyone also experienced that or has any idea of how it should behave over the months/years of use.

Cheers!