User blog comment:Care Level/Ability Concepts/@comment-5544574-20130924102112/@comment-5544574-20130926130213

"Directly affects"

Examples you mention above are the very limit - anything that you could press a button and the effect would always result in the loss of control or hampered abilities for their champion is not really approvable. Trundle, Jarvan IV and Anivia all create terrain but it's not verbatim an obstacle to allies - it's situationally so.

I thought it was one of the clear rules that Riot runs by in regards to other MOBAs.