Yes, it is used in the fprmulation as an emulsion hardener.

Patrick Dignan indicated (B&W notes, June 1972) that a monobath softens the emulsion more than most development processes and has a tendency to produce reticulation, therefore a chemical hardening agent must be added to the formula.

In a monobath, development is a "race" between the developer and the fixer. As a consequence, monobaths usually use a very active developer formulation.