Missing formatter options for field from a custom table defined in hook_views_data()
You are comparing a standard Views field with an entity field. Only entity fields have field formatters. Create a custom entity instead of a custom table if you want to use this feature. For a standard field you have to use the options provided by Views. There is a trim option as well, but it is named differently, trim in the alter section. You see it in Views UI. Try to configure it and check the exported View.