I have no experience with PT design to EC2, but since you have received no reply to your inquiry I would like to see if I can help you out some.
It's also been a long time since I've looked at cracking theory, so I can't even look at this from that perspective.Sorry to read of your predicament with respect to lack of mentor/senior engineer. What bothers me most is that the theory behind sections 7.3.3 and 7.3.4 is almost certainly the same, so I find it odd that $(h-d)$ would have different definitions in these related topics. The fact that it is labelled as "level of steel centroid" isn't very helpful either: is it the centroid of all the steel or just the steel relevant to cracking, which is what's being discussed in this section? Gun to my head, I'd choose the former (all steel), but I can't guarantee that's correct.
If you squint, it looks like the shown centroid is indeed a bit closer to the lower layer, but you never know if that's just an imprecision in how the figure was drawn. Looking at Figure 7.1(a) (shown below), it is not entirely clear which $d$ is being described: if it is the standard $d$, then the centroid would be closer to the lower layer if it is the "outer layer" $d$, then it would be equally spaced between both layers. That possible value $2.5(h-d)$ does not define which $d$ should be used, however.
Looking at section "7.3.3 - Control of cracking without direct calculation", we have equations (7.6) and (7.7) which define the maximum bar diameter for crack control:
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