One fifth of a centermeter is completely wrong, I can't believe this is an article for winter tire tips!!! The author should correct it before this misleading info is passed to innocent drivers and before any death happens due to this article.
2 mm is even less than 2/32nd inch, which can NOT even be safe on all seaon tires during non-winter seasons.
It is recommended to have at least 4/32nd (which is about 5 mm) thread for winter tires, preferably 5-6/32nd (6.28 mm - 7.54 mm). My new winter tires come with 14/32nd (about 17.6 mm) new, I don't think I will even want to drive it to below half of its tread (8.8 mm).