If you aren't trying to make ice, then the energy which goes into making ice is waste. This cuts your efficiency. So, in that case, you do need to include the enthalpy of fusion in your calculations, just be aware that portion is waste. In fact it is doubly wasteful, because the ice reduces the thermal transfer rate and having to stop the compressor means your duty factor is lowered (less water per hour for same size machine).

There are ways to prevent this, although I'm not sure if they would work for your project. Adding salt is a classic, so you can supercool your water while remaining liquid. That's probably not great for drinking water, even with RO. If you can use the melting of the ice as a source of cooling, you can recycle the enthalpy of fusion. It really is a waste and you don't need to pay it. One way to do this is to use the melting ice to lower the heat rejection temperature of your compressor.

However, it may not be worth adding complexity just to cut your energy costs by 15%.