Sure, but this whiffs of cargo cult science. Given that the working conditions, workload and motivation of the "control group" are all heavily affected by the length of the work day of their colleagues in the other group, the interaction effect actually multiplies the variables and the experimenters would actually be more likely to make reliable inferences without it (i.e. measuring 8 hour workday productivity and health indicators as a baseline prior to introducing the 6 hour work day)

The main issue with that is, that the variable introduced by not doing an experiment double-blind can only be measured by repeating the experiment double-blind.