A PL2303 serial-over-USB device is configured to receive-only data. There is an explanation of tty vs. cu here:
MacOS: what's the difference between /dev/tty.* and /dev/cu.*?
That being said, when configuring data collection software, one has to choose either /dev/tty.usbserial or /dev/cu.usbserial. I would like to understand the facts and the decision-making thought for selecting tty or cu.
The distinction only matters when you use a modem that provides the DCD signal and you're interested in sharing the device between two or more processes: one or more that can occasionally call out, and exactly one that wants to answer calls. In practice, it probably matters for historical things like uucp.
For everything that's not a modem or that's not intended to be shared between call-out/call-in processes, you should use the /dev/cu.* as this gives you exclusive access to the device.