Uh-oh, my sanctuary supervisor's obsession with this is being funnelled through me.

Well, as the sanctuary supervisor always says (literally): "Hay is what you eat, straw is where you sleep." Unless you are a rabbit, in which case, you will eat both (because rabbits are weird).

I found the read informative, though my anthropomorphic, and scientifically unaccepted perception on enrichment is that it makes the animal happy, not frustrated. :) (We can't have people thinking animals can experience happiness - that would be uncouth).