Torque3D does its asset loading based on what's visible. You can fill the entire scene with lots of items but until they pass a scene scope query they won't actually be loaded to display. Once it is loaded to display though it doesn't need to be loaded again.
What you're likely seeing is a) the initial position of the camera is causing a number of items to be out of scope on initial load and b) the reflection off the water is causing more items to be scoped when you witness the reflection.
As you mentioned the problem gets worse with heavier scenes. The ideal solution would be threaded asset loading so there is no noticeable stall even if that would result in visible popping as assets finished loading its better than stalling the game in my opinion. A hack solution is to make the first few frames of the scene scope everything so all objects will be loaded, then go back to normal scene query afterwards.
I chased this problem for a little while back when I was using T3D and it's a pain. My problem was that players would spawn, turn the camera and get hit with a 2-3 second stall then the game plays fine after that.