Does Apple repair or replace defective laptops under warranty?

Generally they only repair the computer with the following exception:

The customer has replacement rights for very new machines due to local consumer laws,

Repeated repairs failed to resolve the problem and local consumer laws require replacement in this situation.

Geniuses have workload piled up and are too lazy to accept new repairs.

Special programs requiring replacement.

I've never seen them opening up a device in front of a customer, all repairs are taken to the workshop and finished at a later time, possibly by someone else.