There are plenty of good ports that never got mod tools. Mass Effect comes to mind. I guess they could later, but doesn't seem likely. Maybe they just wanted to be be nice by bringing it over to the PC? They don't need the money, I guess, right? I'm not confusing anything. These companies are out here to make cash. There's no obligation to release tools, nor should they be expected. If they do, cool, if they don't, oh well.
In this situation, AFAIK, none of the engines/systems were developed by LA, so you're latter description fits more appropriately, I think.
This discussion has interested me though. If someone could provide me an example of a popular console game (or any game, I guess), ported to the PC at a much later date, and AFTER the port, received modding toolkits (and not just some lame map editor), I would like to know what games these were. I'm sure it's been done, but I would like to know by who/for what games. LA...anyone.