Civi Export does not use max field length field for Custom Fields varchar

When a user goes to export a custom field from advanced search and using select fields for export. CiviCRM sets the field length for string field types to Varchar(255) even tho there may be a longer db length set in the custom field setting in civicrm_custom_field.text_length

As a partial fix the organisation I'm with I have set the relevant setting which is line 1325 of Export.php in CRM/Export/BAO/ to a higher db length which has solved the problem but I think it would be better if we were using the text_length field.