Find a person
Quite often I know the exact birthday of the person I'm looking for. It seems like that would be helpful instead of entering "Estimated year of birth".
If you know their exact birthdate - you might also know parent or child relationships of the person. Any limiting data that can help the search algorithm find the person should be entered:0
Note also that although you may be certain of the birth year, you are searching for an existing person in Family Tree that may have been created and edited by someone else. For example, someone may have created that person using a 1920 Census record that said they were 15 years old, so the person profile may have been created to say they were born in 1905. You might be aware that they were actually born on 25 December 1904. But in this case, you would certainly want the search to find that profile that currently says the person was born in 1905 -- you wouldn't want to limit your search to persons born in 1904.1