The condensate (water vapor that gets condensed out of the air in the process of generating the electricity) has to go somewhere; if it's not properly handled, yes, I would expect mold.

Mold isn't really your main concern tbh. Instead it would be Legionnaires' Disease.

https://en.wikipedia.org/wiki/Legionnaires%27_disease

Some heat pumps have built-in UV-C sanitization to prevent mold.

You can install an aftermarket UVC light to sanitize to prevent mold in heat pumps, humidifiers, etc