After some more futile research, emailed the Carol Hill, the co-author of Cave Minerals of the World, with a photo. She then contacted Paolo Forti, the other author. Their replies were interesting:
Carol Hill wrote: Off hand, these features look to me like they may have started off as micro-gours, but then maybe later dripping and flowing water down the wall started to transform them into "water spouts" (i.e., build up the chutelike lobes). I definitely feel that they are some kind of composite speleothem form; they don't look to me like they have a biological component.
Paolo Forti wrote:I am pretty sure that they are true microgours, as supposed by Carol.
This kind of forms develops over stalactites, stalagmites, protruding &/or degrading walls every time the deposition leads to monmilk-like deposits ( no matter what kind of minerals is involved: calcite, gypsum, hydrated iron oxides, opal .... and even pure organic matter (mucolites).
The microgour shape is maintained until the material maintains the moonmilk characteristics. Then, when it become less hydrated, the still growing deposit may partially change its shape due to the development of microcorallois or the deposition of layers of normally shaped speleotem (stalactite, stalagmite, flowstone etc...)
Carol Hill wrote:Not sure that a "moonmilk" origin is necessary... I think that the water-spout form may just be due to flowing water being siphoned into a microgour and then downward out the spout.
This answers some questions, raises others. Dunno what "microcorallois" is (microcorallosis maybe? Google doesn't know either), or how "flowing water being siphoned(?) into a microgour and then downward out the spout" creates a spout.
After Forti mentioned moonmilk, I recalled that just around the corner from this spot was a deposit of white slimy-looking gunk that I assumed was fungal. Then a couple of days ago I found another example of the same slime in another cave, this time with a few micro-gours of its own.