As per the Justin's comments on the other thread, here is the flow.
During navigation, the DSA will use:
1. RDN index if "set use-rdn-index = true;"
2. if 1 not set, the normal index (cache-index = <attr>)
In my case, RDN index is not set, so the DSA should pick "cache-index" settings, but its not reading this specific settings. Further investigation is needed.