“Filters synchronizing” is a default feature in the plugin that allows reloading the filters after a filter request. When you select an option in one of the filters/fields, the options of the other fields that will return a result will be kept and the options with no result will be removed. You can see this feature in action in the general overview!
This example here demonstrates disabling the feature “Filters synchronizing”. This means that filters will not be reloaded after filtering markers and all options/terms will be available during the whole filetring process.