The above chimes with my experience getting a 6:15am.
I arrived a bit earlier than planned; south security was definitely open around 4:45am, as were check-in desks. TFW was closed but opened bang on 5am. I was the first one through and then disappointed to find all the people who'd gone through NFT already in the Flounge drinking my breakfast wine

, so I'm assuming that opened bang on 5am or a few mins before.
Think conformance is always 35 minutes, though someone please correct me if wrong.