This seems quite odd as these bags are used most pro-teams, not to mention thousands of other amateur and recreational cyclists around the world.
There is a blurb about this on Emirates website:
Baggage allowances for sports equipment
All sporting equipment including golf equipment, bicycles and ski equipment
Emirates will accept sporting equipment as checked baggage and part of your standard baggage allowance.
Weight Concept
Individual items with total dimensions exceeding 300cm (118 inches) cannot be transported as checked baggage, and must be sent as cargo or freight. There are no exceptions to this rule.
Piece Concept
Total dimensions (length + width + height) of each piece must not exceed 150cm (59 inches). Customers with individual items exceeding above dimensions up to 300cm (118 inches) will be charged an additional fee. Individual items with total dimensions exceeding 300cm (118 inches) cannot be transported as checked baggage, and must be sent as cargo or freight.
For customers with two pieces of luggage in all three classes, the total combined dimensions of both pieces should not exceed 300cm (118 inches).