I've heard that the forces that are exerted on a fork by the disc caliper can bend the blade it's attached to
if the brake mount was added to a under designed fork, not specified stronger for the application..
perhaps this is the case .

meeting low price point rather than good design.

Note: this fork is asymmetric the blade with the disc mount is actually larger
than the one without the brake attached to it.

http://www.tout-terrain.de/2/product...ork/index.html