Connecting to a device console using screen shows no output
Since I couldn't get this working on my mac after multiple days, I decided to try my luck with a Debian 9 VM running in VMware Fusion within this mac. As soon as I made the device available within Debian VM, it was automatically detected and an associated tty* device was created:
# lsusb
Bus 002 Device 002: ID 0e0f:000b VMware, Inc. 
...
Bus 001 Device 005: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port
...
$ ll /dev/ttyU*
crw-rw---- 1 root dialout 188, 0 Dec 29 14:30 /dev/ttyUSB0

Unlike /dev/tty.usbserial within macOS which was open for group others, device /dev/ttyUSB0 wasn't. So, I started screen with sudo:
$ sudo screen /dev/ttyUSB0 9600

And voila, it worked, as per the following screenshot!

I guess this is still a workaround. Checking the screen status (Ctrl-a + Ctrl-i (macos), Ctrl-a + i (Linux)), the latter had CD in brackets, implying signal CD was in effect:

That is the only significant difference that I could spot. Hope this helps others.