All schach is only kosher if placed a certain way.
Let me jump in here to explain lakewood vs. the rest of america. In Lakewood no one would dream of using a mat from home depot, because kaynus is readily available and not too expensive, and there is a lot of social pressure to be as mehudar as possible. Everywhere else, (Chicago, Cleveland, Kalamazoo, Los Angeles etc.) Kaynus et al is harder to get and much more expensive. You'd be paying literally 10 times the price sometimes, for a hechsher, when it's not really necessary. and even the mats with a hechsher have some issues, and there are people who won't use them.
Also in Lakewood the average Jew probably spends 3 or 4 times as much on Arba Minim as anyone anywhere else. יש דורשים לשבח....