Forever a Student
This is something else.Or is this something else? Been a while since my Cervelo days.
Before Shimano introduced the 142x12mm rear hub standard for disc brakes, companies were doing whatever they pleased. Specialized tried bucking the trend and making a competing 135x12 standard called SCS, that failed. Other companies like Cervelo turned to companies like FSA to produce custom one off cranks with different chainlines. That's the case here.
Shimano wants certain spacing between dropouts and certain length chainstays. If a company like Cervelo doesn't want to conform, they'll do something like this, have a custom crank made for them. If you put a normal crank on it will ruin the chain line and according to Shimano will not work as intended. Cervelo doesn't seem to care.
Best answer is not to buy the bike. Wait for them to make a proper road bike with disc brakes, should be coming in the near future.