The outside cylinder heads look to have a spark plug hole plus one other and also a smaller bore than the central cylinder. Yamaha always seemed to like such weird & wonderful experiments/prototypes. Having said that it could just well be AI....
Yeah - it deffo looks like a '5 stroke' as shown in that video. So the induction to the two outer cylinders are the top of the picture (of the head) with the exhaust coming from just the middle cylinder at the bottom of the picture. I'm still unsure why two holes in the outer cylinder and the one hole in the centre cylinder. Perhaps the latter is for another spark plug to scavenge any combustibles left in the exhaust? Interesting - but probably dead in the water what with the push for electric...