Interesting debate. I have read the article by Tim Richardson, but I’m familiar with Piet Oudolf’s work as well. He does actually use decking, water features and other materials like stone paving in many of his designs. Although he uses a lot of planting – he’s not just about planting! (Piet Oudolf’s site). So I think Tim Richardson’s article is misleading.
I think it’s about getting the balance right. Decking is a useful material and has a place in all gardens irrespective of size. It can be an effective foil to planting and paving.