I started to use WebPageTest on a professional project few months ago and I discovered that the speed index was not coherent.
The timeline is:
0%, 0s: Page with a big table taking all the screen
98%, 0.5s: Page with only a small loader
98%, 3.5s: Page with only a small loader
100%, 4.1s: Page with a big table taking all the screen
I do not understand with the changes with the small loader is creating a huge difference between 0 and 0.5s and almost no difference between 3.5 and 4.1s.
The visually complete is 4.1s.
Sadly I cannot show my timeline that is confidential to give you more information.
I hope that you can help me,
Thank you in advance