Understanding PIC32 digital output with open-drain
TRISx basically defines whether the pin is an output pin or not.  ODCx determines whether the output is active both ways or ONLY pulls low.

So you are correct, if TRISx is not set, ODCx does nothing.

Note it's not truly open-drain... it's more Low or Disabled. Because of that it is prudent, when changing the pin mode on the fly, to turn off TRISx BEFORE or while changing OCDx.

BTW: From the shown circuitry, I have always thought that implementation presents a bit of a race hazard between the latch value propagation and the enabling mechanism path. However, I never had any issues with it, perhaps others have encountered some strange behaviours.