I guess the problem is that console.time is called multiple times with the same label. You can easily reproduce this with the following fiddle:
https://jsfiddle.net/q0s1wcgw/
If you just load a single model with GLTFLoader, everything works fine. But when you start to load multiple models at the same time, you are running into this problem.
@donmccurdy I vote to fix this issue. What do you think?