In California, there is a law that basically everywhere (e.g. all apartment complexes) must have a sign that specifies that the compounds used on site can cause cancer or birth defects or whatever. But because the signs are pervasive, they are basically useless. This feels kind of like that.
If you do have an area with known-dangerous substances, and don't put up the sign, you get hit with a penalty significant enough to hurt. If you don't have anything dangerous, but do put up a sign, nothing bad happens to you. So rather than actually check for what's there and put up the sign only when relevant, everyone errs on the side of "better put up the sign just in case".