Each EZIO8SA requires a unique PLM. Several reasons. A Serial Port can be connected to one application (EZIO8SA or software application) at a time. The PLM carries the Insteon address so there would be no way to differentiate one EZIO8SA from another even if the Serial Port design allowed more than one application.
An EZFlora will not run more than one Zone at a time. Normally zones are designed with the source water flow capacity in mind. Allowing multiple Zones could exceed the source water supply.
The EZFlora has a maximum Zone run time for each Zone. This prevents a Zone from running for hours should the automation fail to turn Off a Zone.