The language is perhaps ambiguous. "Sickness absence" can be read as "absence of sickness (thus being healthy)" or "absence (from work) due to sickness". A re

The language is perhaps ambiguous. "Sickness absence" can be read as "absence of sickness (thus being healthy)" or "absence (from work) due to sickness". A reduction of sickness absence can be interpreted as a reduction of "not being sick", i.e. an increase in sickness. But the original reply was perhaps just being pedantic in jest.