I have used fopnu since the beginning.
I never noticed this function until recently.
When I do a search, the next option is "Search More" and when clicked, the existing search results remain and are supplemented with whatever new results come in. After that, the option changes to "Search Again" which removes all results and starts over.
As said, this behavior is new to me. I never noticed it over the years. My recollection it was always just "Search" and "Search Again". Was this "Search More" always there?
Anyway, what are the trigger parameters? I can click the "Search More" button as soon as the initial Search finishes, and it will always find more results. So why were these not found on the initial Search? They had to be there, online at the time.
What are the limitations of the initial Search that are addressed in the Search More function?
I think I discovered part of the behavior.
It appears that the search pauses once there are 1000+ results.. sometimes 1004, 1009, etc. Then it provides option to resume the search, to "Search more".
I noticed that when a search was 968 or so, there was no "Search more" option. Just "Search again".
Seems like it is a search flood protection.