Hope my experience puts an end to this issue. I recently had a run in with an "overly zealous" Apple Genius in replacing my MBP "other" Apple component, Genius discovered that I had a OWC data-doubler. He then sternly informed me that I am going to note this against your AppleCare so when the motherboard malfunction, you CANNOT claim warranty as it has been void and that other things will be covered. But I have 16GB OWC RAMS and Samsung Pro SSD and he had not noted that against my Applecare warranty? Strange.
After few days of global discussion, and had a 2nd chat with Apple Tech Support and Applecare and both confirm that 3rd party devices are allowable as long as they comply with Apple specs. No more that a USB device is plugged into MBP externally or internally. HOWEVER, that 3rd party device MUST NOT be the main causation to the malfunction claim under warranty. If the causation is too remote to be the main cause, Apple assess the matter in a case-to-case and the intent of the cause. So as far as my OWC data-double is concern, it's a green light from Apple Tech Support and AppleCare.