Alright, here's a crapshoot but here goes.
The greneng form here looks to me like a more overtly botanic version of the element mentioned in the thread "Gustav's Discovery" -
http://www.vikingsword.com/vb/showthread.php?t=22975.
This element was one that appeared in some keris older than 1700-ish.
If that's true, then for this element be repeated so many times on this keris without having a single conventional ron dha between them would make this keris an exceeding rarity, if not totally unique.
As Alan has suggested, the keris abides by conventions, especially during a historical period that was organised strictly along social status and the pervasiveness of religio-spiritual meaning.
It's hard to me to believe that this supposedly very old keris is so unique and breaks so many contemporaneous conventions.
Perhaps whoever made this wanted to make a point by including a greneng and ron dha nunut made up entirely of an element that only appeared in older keris (and even then only sparingly).