During the Q&A portion of John Mueller’s hangout on 09/17/2021, one webmaster was concerned about the regrouping of approximately 30,000 pages on their site.
This brought the average LCP for those pages up approximately 0.9 seconds, even though they were all at around 2.5 seconds below the threshold.
The webmaster was looking for information about how to help them establish more of their pages under the 2.5-seconds loading threshold.
John explained that Google doesn’t have a clear or exact definition of how they do grouping. This is something that evolves over time and depends on the data that they have.
If they have a lot of data for different kinds of pages, it’s easier for them to say how they will do grouping for those pages.
The question and answer occur at the 35:40 mark in the video: