which isn't true at all, i have seen this video getting discussed at a few big photography pages (slrlounge or fstopper i forgot and also some other people sharing it). the problem is, a f2.8 will still be f2.8 regardless the sensor size. a phone sensor with the exact aperture and shutter speed + iso will produce the same result as a FF with same settings.

it's not that a f2.8 on a m43 is f5.6, it's just the amount of DOF the m43 produced is only 1/2 to what FF produces. imagine cropping a f2.8 picture, will the picture become darker at the end/ the exposure change? no, because it only crops the image, same with smaller sensor.