I actually think it might depend on your climate. Here in winter I'm struggling to keep the plants warm enough and without heat mats can get root rot in the phals and S/H cools the roots too much in the winter here. I wouldn't try ice for that reason and purposefully warm the water very slightly... however if you are in a warmer climate it probably does no damage to the roots.
I think the key thing is that the technique promotes restricted watering and not drowning the things. Personally I prefer to manage my watering in other ways, but I can see how this technique would work given the right conditions.
That having been said, I've been suspicious of some of these comments from people who only ever make one post... but I have a suspicious mind as well