See https://wiki.openstreetmap.org/wiki/Any_tags_you_like 

and
https://wiki.openstreetmap.org/wiki/Good_practice#Don't_remove_tags_that_you_don't_understand 

and 
https://wiki.openstreetmap.org/wiki/Creating_a_page_describing_key_or_value#Who_can_edit
("The wiki documents what is used in practice; it is not a place to define what "should" be mapped"). Thats reason why those tags are not documented at the time. 