For some reason (see screenshot) - my attempt to mask using the MatLayerBlend_TINT node is acting up. You can see in the preview window on the master material, the mask tint is working correctly. However, on the instanced version of this master material, it instead tints the entire material, ignoring the mask completely. Confused.
I’m willing to go into more detail but for the sake of the simplest explanation, I kept this short and sweet. I will answer any inqueries from anyone willing to help me troubleshoot this.