270,000 km. And fast charging about 3 times a year.

If I were to guess, the main factor harming the battery is my garage gets pretty hot in the summer (37 or 38C)

I'm not even sure how to calculate our deg! Same, 2018 3 long range. I think they advertised it as 305mi but some time later increased the capacity of the car to 315mi; I max charged it to 314 once but never quite saw that 315. I think we're around 273 as max now so 89.5% of the original quoted life, 87% of the "updated" life. Car has 115k miles, ~ 185,000km.

There was about 2 years of rapid drop off that I experienced and I don't exactly know why.

That is quite high mileage. I'm certain someone smarter and less lazy than me can calculate the amount of expected cycles that the battery would have seen.

Do you leave it fully charged for long periods of time, or do you discharge it down to empty or nearly empty quite regularly?

I charge it to 70% and leave it there most of the time.

I don't often fully discharge, that's bad for the lipos. I usually keep a 40-70 range SOC.

I agree, reads like carefully crafted FUD.

What possible motivation would I have to spread FUD about my own car?

To me this is perfectly reasonable degradation after 7 years of ownership with the number of miles I have.

There is also just an element of luck that's involved. Batteries degrade at different rates and there's not really any accounting for it.