It has nothing to do with anti-icing gear. As your cited source says, the reduced MTOW includes “No physical changes to the aircraft”.
The reason is just a different classification of aircraft between US and Europe (which makes a difference in landing fees, insurane etc). In Europe, one of the limits is 2t, so often an aircraft that has technically a bit higher MTOW (for the American market) is available in an “artificially” limited version to 1999kg.