While Dinotte annoyingly isn't listing lumen output for their 300l rear light, here's the page for the 400l -
400L Taillight (LI - Endurance series (lithium-ion rechargeable))

Where it says "300 Lumen Taillight".

I posted a screenshot from the video someone posted of the previous (and dimmer than the 200) 140L where it's a brighter light source than the car tail lights -


I find it nearly impossible to believe that a single car tail light is putting out 300 lumens, seems like by your estimation it's putting out more than 300 lumens - something I find even more impossible to believe. I used to ride with 200 lumens - it was a lot brighter than my car tail lights. If it's somehow putting out that kind of power, it's definitely doing something to make it non-blinding that bike lights are not doing.

Car lights don't exist in a magical separate reality, they use lights just like bike lights do. And modern bike lights don't have a problem putting out similar or occassionally greater power than car lights.