you could have done simple test of swapping in your old pre-install RAM to find out.
RAM kills mainboard? I probably want to see more facts on this before I believe it.
Anyway, Apple's threat is FUD. There will always be faulty RAMs (Even if we assume they are correct in saying its a RAM problem, which may, or may not be true in the first place). Even if you spend 300% more to buy from apple, they just grab from other RAM makers, you still have that risk of faulty RAMs.
PS. Always reinsert original RAM before you send it back for repair, so they don't give you may-be-false excuses. Third part RAM probably is the easy target since Im sure they would love to blame anything but themselves whenever possible.
Yeah...i've never heard apple saying...oh third party RAM in here...problem..They will have issues though if you damage something when installing it. If you read the guide though...watch youtube videos...you will know how to upgrade RAM. If a problem happens..just put the old RAM back.