Quote: "Does this means that those games were created with a version of FPSCreator that wasn't version 1.04? "
Yes. The latest updates have improved the loading times, but as Airlide said above, levels with a lot of content are going to take considerable time to load.
Level optimization is an ongoing process, and only a few here are currently working to learn and use it. The software is progressing quickly and we will continue to see improvements in both loading and play speeds I'm sure.
I'm sorry, my answers are limited. You must ask the right question.