That’s probably one reason to do it, but the more common reason is to simplify the oiling system to increase reliability. The balance shafts are there to cancel out vibrations from the engine. They do this by spinning at twice the speed of the crank. When you’re revving to 7.5k like a lot of us with built motors are, those big lumps of metal are spinning at 15k. There have been a few cases of them seizing and causing problems like in this engine. I’m not sure if they seize on their own or if that is a result of something else such as the oil pump drive chain snapping. Either one will cause the other, so there is no way to tell which happened first.
By removing the balance shaft assembly, you also gain ~2 liters of oil capacity IIRC. The only real cons to doing the 1.8 conversion is the cost of parts and a marginal increase in NVH. Some people have had oil pressure issues with the conversion (Mec wiped a main bearing) but others have been successful. I’m not sure what the cause of that is. I decided that I wasn’t willing to get experimental with an engine I just spent nearly $6k building. Maybe I’ll consider it down the road though.