Leaf and some flower buds have their own stored supply of energy nestled at their base. You've placed the cuttings in water, which has activated this leaf formation and their consumption of that energy. It's also the reason why leaves growing on a cutting in soil is not a reliable indicator that roots have developed. Once the leaves develop, they will provide food to the cutting via photosynthesis, helping it to produce roots.
I'd suggest that if you planted them in soil, you'd have as much chance of them taking off as any other cutting. It sounds like you had good luck last year, though. You might like to dip their ends in some Yates 50ml Red Clonex Rooting Hormone Gel to increase your chances.