No, the word port didn't confuse me, it's just that I see a lot of people on here throwing around words like that without the fairest conception of what they mean in practice.
First of all, it's germane to this discussion that I too am not a programmer, but I DO work with very highly skilled programmers, so I have some idea of the complexities involved.
The PSX2 has custom hardware. For everything. Part of the challenge of writing good games for the PSX2 seems to have been in learning how to get all these specialist hardware components working as tightly as possible. Writing a game for the PC is very different - the primary focus on PC is in dealing with the huge range of differing machines.
When you write a game for the PSX2 it's a very different challenge, and it requires a very different engine. The emphasis is on optimisation and polish.
When you write a game for the PC the challenge is scaling - the act of getting the game to run firstly on machines of differing horsepower, and finally on machines of massively variable internal architecture. Then you have the variety of Operating Systems. I could go on, but I'm sure you've got the point.
I imagine that the "PC" version of GTA III is, in fact, a spin off from the X-Box conversion. So call it 7 months to perform the X-Box conversion, and then modify it to run on a variety of PC configurations.
I don't know how much of the engine will have had to have been recoded FROM SCRATCH to do this. Sometimes the specifications involved are so different that the art assets have to be recreated FROM SCRATCH. Sometimes the Engine has to be rewritten. All you get is a mature design document and all the speech and cutscenes completed for you. I'm certain that everyone would admit that the speech and cutscenes are NOT the major part of a games development?
7 months is not too long for a conversion of this type - the big difference is that it's been done consecutively to the primary version, instead of concurrently.