While the pic attached is of a 5 chain engine and yours is a 3 chain the mechanicals similarities should be evident.
On these engines the chains have a "driven"(under tension) and a slack side that the tensioners control. The vario cams can move ~23 degrees in relation to the crank and you see how short they are. How many degrees backward does the crank move before all the slack is pulled out of the crank to IMS chain and the camshaft drive chains on the slack side? JFP might know but it would be considerable. Obviously enough to interfere with piston travel.
