Yes, any BUCK feedback pin that is not being used for the BUCK feedback can be used as a voltage monitor. Unused feedback pins include FB_B3 on a 3-phase or 4-phase BUCK and FB_B4 on a 4-phase BUCK. Also, any feedback pins on an unused BUCK can be used as a voltage monitor. The monitor target voltage can be set using the BUCKn_VSETx register corresponding to the BUCKn_VSEL bit setting. And the window can be set by the BUCKn_PG_WINDOW register. The monitor can be enabled by setting the BUCKn_VMON_EN bit.
If the monitored voltage goes out of range it will cause a BUCKn_OV_INT or BUCKn_UV_INT. The PMIC's reaction to this interrupt can be set by the BUCKn_GRP_SEL and corresponding x_RAIL_TRIG bits.