FCP is lower than TTFB/server response time in PageSpeed Insights

### FAQ

- [X] Yes, my issue is not about [variability](https://github.com/GoogleChrome/lighthouse/blob/master/docs/variability.md) or [throttling](https://github.com/GoogleChrome/lighthouse/blob/master/docs/throttling.md).
- [X] Yes, my issue is not about a specific accessibility audit (file with [axe-core](https://github.com/dequelabs/axe-core) instead).

### URL

https://

### What happened?

Hello,

I posted a question about this in the Chrome UX forums and was directed here to file an issue.

Last week, I ran a URL through the Pagespeed Insights tool and it reported a 2500 FCP but a 3500 server response time.

I was asked not to share the URL by the site's owner but I'm sharing a snippet from the report below:


Just to clarify, when does FCP and LCP start measuring? Does FCP include the TTFB, and does LCP include the TTFB as well as the FCP?

Thanks all.

### What did you expect?

I expected the FCP to be inclusive of the server response time but this report indicates the FCP was shorter.

### What have you tried?

_No response_

### How were you running Lighthouse?

PageSpeed Insights

### Lighthouse Version

Lighthouse 8.4.0

### Chrome Version

hrome 92.0.4515.119

### Node Version

_No response_

### OS

MacOS

### Relevant log output

_No response_