You don't have a low TA by itself. When you lower the TA, you raise the CH to compensate (or target a higher pH or both). You make the saturation index near zero (you can use The Pool Calculator to calculate the index). The saturation index calculates the saturation point for calcium carbonate and that is what protects plaster surfaces. TA alone is irrelevant. It is the combination of pH, TA and CH (plus some other less important factors) that determine whether there will be scaling vs. dissolving of plaster vs. a perfect balance.

Forget "low TA" or "low CH" causes dissolving of plaster just as "high TA" or "high CH" causes scaling. It is the combination as determined by the saturation index that determines the tendency (it does not determine the rate).