You simply do a little research before you buy USB adapters to make sure it has proper drivers/support for your OS.
You are making it into a bigger deal than it needs to be.
Thanks for the good laugh that I had when I read those words.
Seriously though, it was a big deal, especially since I had done my research prior to my purchase and had the proper drivers.
Keyspan tech-support talked me through a self-test of the device and then claimed that, since the Keyspan passed the self-test, it was working as designed.
Gee, that's great but it is not running my AIM-4170.
These virtual ports can be configured to any type of handshaking, comm port # and baud rate via a few mouse clicks.
I totally agree with that sentence and I've been there, done that many times with the Keyspan but only had to do it once to the Radio-Shack.
BTW, as I understand it, an adapter designer has a choice of using a Prolific-chip (bad choice) or a FTDI-chip (good choice).
I would suppose that you were fortunate in getting an adapter which used the FTDI-chip.
From my experience, information like that is not to be found on a web-site or any container-box....neither for Keyspan or Radio-Shack or anywhere else for that matter.
Also, from another group, I have learned that a RT Systems adapter RTS-03 for $23 is universally acclaimed to work in all applications (disclaimer: I have no financial interest in the company). I just can't bring myself to try it out.

73 Jerry km3k