So yes , there is a correlation between ddpm fluidity and CSR in coking coal. Generally, there is a negative correlation, meaning that higher ddpm fluidity tends to correspond to lower CSR. This may be because coals with higher fluidity are softer and flow more easily, which can lead to the formation of weaker coke with lower CSR.
Possibly explaining why kestrel & Gregory suffer... it's important to note that the relationship isn't always perfectly linear, and other factors can also influence CSR, as you say, ash content. Both those mines being at the southern end of the Moranbah measures, effectively being called German Creek measures, is a good clue. Tgat part of the basin had a transgression/regression period creating the McMillan formation. This different burden structure may be why we see weakening coals to the south of Saraji... which is where this McMillan formation extends.
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