Do you have evidence that the variation in genome size among multicellular organisms is not variation in waste?

I haven't made a claim that strong. To the extend I made a claim it's not all variation in genome size between multicellular organisms is due to different amount of waste.

And no I don't intend to claim something that's out of consensus in this topic. To the extend I might differ on this topic from consensus consider that to be errors.

If I remember right then one reason for plants like grasses to have long genomes was to have multiple copies of genes to speed up protein production.