Does the Any-Grid PSW-H inverter pass AC input through to the AC output, thus retaining phase information?

Yes, since the Any-Grid PSW-H does not rectify everything to a DC bus (as that would incur high efficiency losses). This means that if you have multiple units in parallel on one phase and multiple units on another phase, they cannot have differing AC input sources. For example, one phase cannot be connected a generator and one phase to the grid at the same time. If an AC source is used, it must have the same number and angle of phases as the Any-Grid PSW-H cluster.