Results match the current search
Without it
Every answer is shown as it arrives, so a slow answer to an old query covers the newer one, and the choice turns into its raw value once the results change.
With it
A search response is shown only if it still belongs to the current query; a response to an older one is ignored instead of replacing newer results. The option you chose keeps its name in the field when a new search no longer returns it, and a value set in advance shows the label given in items before the first search answers.
Without it
Every answer is shown as it arrives, so a slow answer to an old query covers the newer one, and the choice turns into its raw value once the results change.
With it
A search response is shown only if it still belongs to the current query; a response to an older one is ignored instead of replacing newer results. The option you chose keeps its name in the field when a new search no longer returns it, and a value set in advance shows the label given in items before the first search answers.