While the name is clever (basically Japanese ghosts) I don't really think it fits a Tyranid Fleet.
For example, Behemoth is biblical/Jewish religious figure destroyed by God during the time of creation, and is commonly associated with large, brutish animals like hippos, water buffalo and elephants, which is related to how Behemoth was the first Nid fleet, wiped out in the beginning of the Tyrannic Wars, and was basically a smash-and-grab(the biomass) kinda strategy.
Kraken is a mythological sea monster analogous to a giant octopus, with many tentacles, kinda how Kraken spread splinter fleets over a large area.
Leviathan is a religious beast related to Behemoth, with many connotations depending on source (this wikipedia page really shows how much though the writers put into the name of the Tyranid fleets, or at least, the big 3:
https://en.wikipedia.org/wiki/Leviathan) but in short, associated with the end times, is a crown prince of Hell in Lavey Satanism, is a prince of hell in various sources, etc, which is really poignant as HFL is the most deadly so far and looks to be the end of Humanity as it steamrolls towards Terra.
In short, I think the name is unique but not in keeping with the other Hive Fleets (who all follow the names of Biblical-level monsters or greek myth monsters such as Kraken, Hydra, Gorgon, etc), with the exception of Jormungandr who is a world devouring snake in Norse (accurate, really)