Maybe this image helps a bit, offset rim helps to make the hub-rim-spoke triangle more even and allows for more even tension between the drive and the non-drive side of the wheel, which makes a stronger wheel. As @Emyr pointed out a longer freehub body results into a less even tension than a 'normal' shorter freehub body. An offset rim helps to compensate
tldr left triangle is more 'even' and therefore stronger
Thank you. Let me rephrase, none of my 10 speed wheels built on not offset ever needed retruing before replacing. Maybe a bit leading now: the wheel builder wouldn't really need offset to achieve the same result with 11 speed?
Maybe this image helps a bit, offset rim helps to make the hub-rim-spoke triangle more even and allows for more even tension between the drive and the non-drive side of the wheel, which makes a stronger wheel. As @Emyr pointed out a longer freehub body results into a less even tension than a 'normal' shorter freehub body. An offset rim helps to compensate
tldr left triangle is more 'even' and therefore stronger