You are right about the PWM dimming - but it's a better alternative to the lack of dimming of CFL bulbs.
The 20k hour figure likely does figure in "lumen maintenance" - although Switch maybe stating a "consumer lifetime", the mean lifetime of the product, they are required to provide a lumen maintenance figure called L70 - the time it takes for a 30% reduction in light output. Chances are these light bulbs just broke before reaching that target, and the consumer lifetime is more useful to the market at large.
And, yes, the warm color with high CRI is the hardest LED to make - that's why they're waiting until next year to try and offer a warm white 100W equivalent bulb.
The 20k hour figure likely does figure in "lumen maintenance" - although Switch maybe stating a "consumer lifetime", the mean lifetime of the product, they are required to provide a lumen maintenance figure called L70 - the time it takes for a 30% reduction in light output. Chances are these light bulbs just broke before reaching that target, and the consumer lifetime is more useful to the market at large.
And, yes, the warm color with high CRI is the hardest LED to make - that's why they're waiting until next year to try and offer a warm white 100W equivalent bulb.