i think it does - it's basically to protect the threads from rot and bad stuff like that. challenge doesn't particularly proactively recommend treatments but dugast recommends aqua sure for their tubies.
that's true actually - they opens are polyester threads now, not poly-cotton or silk. i guess threads are less susceptible to rot, but perhaps there are benefits to prevent de-lamination and protect the threads from abrasion. we'll try to get challenge to weigh in here.