The recommendations you linked to aren’t for vegans. They recommend dairy over legumes. And indeed I eat a lot more cheese than lentils.
But since dairy isn’t an option for you, you have to settle for the next best thing. And in order to do that, you need more specific information than what these recommendations provide because as it is, the foods vegans should eat for protein are basically all in the “eat in moderation” category.
Based on the limited information I have about meat substitutes, the ones based on plants contain a good bit less purines. Yes, Quorn products contain less purines than the really dangerous stuff like yeast or anchovies. But that doesn’t mean you should disregard the difference between Quorn and plant-based products.
In my opinion, the only rule you have to follow in order to be safe purine-wise is to stick to plants. There’s probably no need to make it more complicated even though there are a few dangerous things unreasonable people could in principle do with plants. At first I didn’t think you’d have to follow any rules because I figured that as a vegan you’d only want to eat plants anyway. Goes to show how little I know…