Here's what Akira has to say about it:
"I was almost gassed just walking into the cage. Whatever, I'm a professional and I got the job done. I had double vision the whole fight. I actually don't remember anything from that fight. I just remember two things. One is the knockdown. The other was that when he had me in a heel hook it wasn't there. It wasn't in. If you watch the video again you see my knee pop out because he slipped. He lost his grip. I was thinking 'holy •••• he's got it!' I changed my mind the moment he slipped. I've watched it maybe 100 times and I know for myself that I never tapped. Herb Dean has refereed thousands of fights and he didn't see a clear tap. Usually it's a horror scene when somebody taps from a heel hook. People start screaming and crying. I raised my hand and tapped one time on his thigh but it wasn't one of those dramatic taps like a metal drummer. It slipped out and I just went up on him. I would be honest and say I tapped if I did. I know the feeling that went through my body saying 'this is going to hurt, I'm going to tap.' But then I got out. One hit and then I'm out."
Here's a gif of the tap: