The best way to turn it off is to specify an expression for naming filled forms: https://docs.getodk.org/xlsform/#naming-filled-forms This will generate the name based on form data and make it read-only. You can choose a unique identifier for the submission that is not personally identifying for the participants. For example, you could do something like concat("Fav color: ", ${enumerator_id}, " ", ${datetime}) if you have enumerator_id and datetime fields in your favorite color form. This name is used throughout Collect where filled forms are listed and in Central on the submission details page.
You can alternately configure Collect to hide the manual naming option without specifying a name expression. To do that, go to Settings > Access control > Form entry Settings and uncheck "Name this form". This means the form name will be used for every filled form and the instance ID (e.g. uuid:123e4567-e89b-12d3-a456-426614174000) will be used in Central.
We will be removing manual naming of filled forms in Collect soon as part of broader improvements to form finalization. We agree that it's confusing and analytics show it's used by less than 5% of data collectors.