The link doesnt work. Also as long as the mat is thick enough it will be fine. You just don't want the wire cutting into the mat with the weight as that could scratch the tanks.
Another thing you could do if you are worried is to cut a piece of plywood that is same size as tank then put that on the shelf, then garden mat, then tank to keep it looking clean. 1/4" thick plywood is more than enough and you can get a 4x8ft sheet at HD for $20 which would be enough for a ton of tanks.