WPT does not apply CPU throttling to Lighthouse run

**Summary**

I tried some tests on multiple cases with Speedcurve and Webpagetest and found some troubling behaviors :

I used the configuration for CPU throttling and set it to 4, 6 and 12 on the same page with same 3G connection configuration and got performance score of respectively : 38, 43 and 49.

I expected a completely different results with a lower score as the throttling get higher.

I found that when using the throttling I have errors on javascript and CPU related diagnostics:
- JavaScript execution time Error!
- Minimizes main-thread work Error!
- Third-Party Usage Error!
It may or may not be related but what I thought when I saw this is that the when CPU is slow, execution of javascript and main thread go in timeout mode .... and can't achieve any measure.

It could be nice to have more information on that when using the tool so user can understand what happens.

Best,