The writer said it's two years old. You either get 2 years or 800-1000 charge cycles before that battery will hover around 80% degraded. That is in line with what I have seen for the past few years. The battery is fine. They just have had heavy all day usage apparently. They have used up most of its usable life. The battery isn't dead only heavily degraded after two years.

The article says it's covered by AppleCare+, but the author can't deal with the multi-week downtime that sending the machine in would cause.

Have I had to replace batteries, yes. Have I had to do it at the same frequency no.

Not trying to be critical of you, just curious why the batteries get cycled so much. I have used machines heavily over two year periods but perhaps the difference between they were generally plugged in so I was not cycling the battery as quickly.

FWIW my M1 Air 2020 is at 93% health. We could speculate about the potential root cause of this different (I always use optimized charging and the author appears to have it disabled on their screenshots)... but it's quite more likely that it's simply bad luck of the battery draw.