This has been discussed before here, and this design flaw has been confirmed by Glenn Block, the coordinator of the CSL.
Fixing this is a big breaking change, but not changing this IMO is not really an option, since the current implementation makes the abstraction unusable. For this reason the CSL Adapter for the Simple Injector does not inherit form the ServiceLocatorImplBase. Although the behavior of the Simple Injector adapter correctly implements the IServiceProvider contract, it is still unusable, simply because all other implementations break the contract.