Even though I could not load the PDF file: as I understand it, the attribute describes the angular deviation of 180 degrees (linear lines) of the power cables. This has not yet been included in the descriptive attributes of a power pole. I would like to note three things: The key should be written with lower case letters as usual and the value should be in degrees with decimal places. Furthermore, you should document this key in the wiki (especially the postfix LT, RT). 
From my point of view, it would still be questionable whether the classes mentioned in the Twitter post are not sufficient.