If you wanted an un-editable title that you add when creating the field you could add a new field setting https://www.advancedcustomfields.com/resources/adding-custom-settings-fields/ but I don’t think that’s what you want.
The only way to have a title that can be edited when adding the gallery would be the way you suggest. Either that or building a custom field type based on the gallery field, adding a new field and then storing the information in a different way than ACF does it. https://www.advancedcustomfields.com/resources/creating-a-new-field-type/. ACF stores an array of post IDs for the images in the gallery. There is nowhere to store other information.
