Redundancy is efficiency. No ship would operate with exactly 75 people to cover 25 stations in three shift. Either some of those stations are redundant, or you have more than 75 people. Otherwise, one illness or injury would bring down the whole system.
A switch to shorter shifts would reduce redundancy on each shift, but each worker would get more rest and be less likely to burnout or get sick, even if they have to pick up occasional double shifts until they can take on more crew.