When you apply heat or steam to acrylic items, it 'kills' them, partially melting the plastic fibers and that indeed is permanent. What this article shows is nothing different than how you'd block wool fibers and while they may look good right after take the pins out, I don't think it's going to be permanent at all - it will have to be done again after you wash it. Washing and drying creates enough steam that it'll keep it's shape and size and relax the stitches which is all you need to do to acrylic. Anything more than that is for people with too much time on their hands...
sue- knitting heretic