The waste symbol is to clarify the difference between colorless and mana of any color.
http://magic.wizards.com/en/articles/archive/feature/oath-gatewatch-mechanics-2015-12-28
lol i know what waste colorless mana does, at this moment there is nothing to be cast or abilities used that require waste colorless mana , just use the land produced colorless. Again the diamond shape waste colorless mana is only on Eldrazis and their abilities used that require waste colorless mana. So "far" in these spoilers for shadows over innistrad it is clear that not a
single card requires the diamond shape waste colorless mana. So why in this set of shadows over innistrad would I need a card that produces diamond shape waste colorless mana when a basic land works perfectly fine?
This diamond shape waste colorless mana has to cast or do some ability that basic land colorless mana can't.
Basic land colorless mana couldn't cast kozilek while diamond shape waste colorless mana could.
Now you could say shadows over innistrad's diamond shape waste colorless mana could produce kozilek. Ok, I'd give
you that but BFZ and OTG both have way better diamond shape waste colorless mana producers.
Now come full circle, diamond shape waste colorless mana producers only cast " Eldrazis " and " helped activate abilities of eldrazis". Land producers produce land colorless mana that "can't" do that.