it is not, do not kid yourself... first of all 43/m43 is not 2 crop (the size of the actual imagimg area of the sensor is not 4 times less than FF, but 3.7 times less - and that is only if you believe that part of active pixel area in FF sensor that makes its way into a raw file for an image is indeed 24mmx36mm... which is not) and then you 1.5x crop if you will find the actual sensor specs is less than wikipedia-total size of the die size (try).
PS: example : kodak 43 size sensor (kodak likes the precision in measurments) = http://www.kodak.com/ek/uploadedFiles/Content/Small_Business/Images_Sensor_Solutions/Datasheets%28pdfs%29/KAF-8300LongSpec.pdf
active pixel area = 17.96mm (H) x 13.52mm (V) with 3326 (H) x 2504 (V) active sensels, out of which 3264 x 2448 sensels make it out to the picture (see Olympus cameras w/ that sensor)...
( 17.96mm x 13.52mm ) * ( ( 3264 x 2448 ) / ( 3326 x 2504 ) ) = 233 mm^2
give FF sensor a favor and assume it really makes the image off 24mm x 36mm, so 24 * 36 / 233 = 3.7... that is not 2 stops... and there is not 1 stop between 43/m43 and APS-C, but way less
Leaving aside the technical argument (which I've no idea if it's correct or not)
I've shot extensively on 35mm and APS-C and yes I've used 4/3 cameras too.
You can clearly see the micro 4/3 shot is near to the FF Canon at around f4 when the Olympus is at f1.8, they're close that's near enough to 2 stops. APS-C to full frame is just over a stops difference. It can't really be argued that APS-C doesn't fall "in between" FF and micro 4/3 erm for obvious reasons..because it does!
Now you might not care, you can use faster lenses on micro 4/3 to get there shallower DOF, as you can on APS-C
You could argue that the DOF isn't a big difference micro 4/3 to APS-C, but the reality is somewhat more stark.
DOF is one thing, focal length another. The effects of background compression with longer focal lengths also come into play. A 50mm on full frame, you need a 25mm on micro 4/3, and just under a 35mm on APS-C. That's probably the reason why it's not as easy to get pleasing blur on micro 4/3 even using a 50mm lens on micro 4/3 you have an equivalent field of view of 100mm, and of around 75mm on APS-C. You're effectively moving back with APS-C and micro 4/3 to get the same framing (hence distance to subject DOF)
I'm not arguing you can't get shallow enough DOF on micro 4/3, I'm suggesting that it's not as easy as APS-C and obviously full frame has the creamy blur crown here. Nor do I subscribe to the "Must have blown out background super creamy" for every shot. Like any photo technique it can be overdone and overused.
What I do say is that it's not accurate to state that the DOF differences micro 4/3 to APS-C are insignificant, clearly to some they are significant enough.
Anyway despite some nice lenses, I've yet to see a convincing argument why people should pay near full frame prices for a micro 4/3 body. Sealing or not that's not realistic in the market place.