Yes, the ADS1118 circuit is right out of the data sheet and that would be fine except they made one BIG mistake.
The thermocouples are connected to terminals on the wiring board at the extruders and then copper wire is run from there to the ADS1118. This means that the cold junction to be used in correcting the temperature starts at this interface. The ADS1118 is using its internal temperature sensor for the cold junction temperature.

We do not know what FF is doing in the software (they may have put in some kind of fudge factor) but I do know (have measured) that as the extruder area heats up, the reported temperature goes down. This error is directly related to the difference in temperature between the ADS1118 and the extruder wiring board.

In my testing, I found that when extruder temperatures were at or below 230°C, the error was not significant (<2°) and constant once things had warmed up. But when the extruder temperatures were set higher, the error was significant (8-10°) after about 30-45 minutes of printing and KEPT CLIMBING. These tests were done with the door closed but the top off as I have seen at least one totally melted extruder carriage.

What happens with this error is as the cold junction temperature increases, the temperature reported to the processor goes down so it increases the heater on time. Theoretically it is possible that this could lead to a runaway situation where the processor kept the heater full on trying to get to temperature, not knowing that it was already too high.

The best work around is to replace the thermocouples with those from the Creator Pro and run the thermocouple leads directly to the connector on the main board.
Graham