segmentation_type not working for all GET stat calls

[imahgrefteh]

All the Twitter ad api analytics calls, allow the user to pass a segmentation_type My questions are regrading the analytics with SEGMENTATION_TYPE.

For reference here is the documentation: https://dev.twitter.com/ads/analytics

1. Why does the segmentation_type EVENT not work with any of the Twitter ad API analytics:
   https://dev.twitter.com/ads/reference/get/stats/accounts/%3Aaccount_id/campaigns
   Below is an example of calling the anyaltics with SEGMENTATION_TYPE event:

   https://ads-api.twitter.com/0/stats/accounts/8nm/promoted_tweets/1ydz?granularity=DAY&start_time=2015-10-01&end_time=2015-10-02&line_item_ids=14n08&segmentation_type=EVENT
   

Here is another example:

 https://ads-api.twitter.com/0/stats/accounts/18vk3ll?granularity=DAY&start_time=2015-10-01&end_time=2015-10-02&segmentation_type=EVENT

Please note I am using dummy account information for discussion purposes.

2. How can I tell which call segmentation_types will work with which calls.
   For example

   GET stats/accounts/:account_id/campaigns

allows the SEGMENTATION_TYPE of CITIES but not LANGUAGUES?