Well pipe(), despite being a great extensibility tool, is not a "flow-reuse" abstraction, as it (mostly) just works as a transformer of (mostly) one observable into another. a reactive flow is a directed graph in general and an inverse-tree in RxJS.

of course you can simply re-use parts of the inverse tree using functions from multiple observables to one, and the main issue for this is basically the inverse-tree model limitation, as can be observed in appearance of convention-breaking and uncomfortable pipes such as partition.