If we use a single field for search and autocomplete, then the parameters used for autocomplete will be added to it on every request. Since it is not necessary to display duplicates during completion, it is set in the parameters not to display them. However, if we pass the value as a views parameter, then we need all the results.
Create an index with a fulltext field
Set autocomplete for this field
Create a search api based view page and add the field created in the index as exposed filter
Load the view page and start typing the text you want to search for in the field
Select a value that you know will be found in more than one result