So different, our experiences. I agree the older ones didn't smell as bad, and the smaller ones don't either. Maybe it varies from factory to factory? Obviously the larger the mat the more treatment it needs, but I guess we'll never know.
Anyway, I went to JoAnn's and bought the 18x24 Fiskars mat and no odor. If you stick your nose right on it there is a smell, but it isn't putrid. Had it in my bedroom last night and no smell. Yay! I did check the larger size Olfa mats and could barely bring them to my face because of the smell. Must have looked funny - "check out the crazy lady smelling mats!" lol.
Anyway, so far so good! Time to wash fabric and sewwwwwwwww!