I can't find a way to do this so I'll post it as an idea.
When setting graduated color symbols, the upper and lower limits are first set by natural classification. At this time, the minimum value is set to the minimum value of the lowest range, but although there was a way to rewrite this in Python in ArcMap, it is no longer available in ArcGIS PRO, which is a problem.
For example, if you import layer A with a symbol with a minimum value of 5 into layer B with a minimum value of 1, features 1 to 4 will no longer be displayed. To avoid this, ArcMap used Python to set the minimum value to "-1000000".
ArcMap has a property called "classBreakValues" that returns all the range values in a list, making it very easy to set the numerical values for the range. However, in ArcGIS PRO, the only way to change the numerical values in the range is to change the upper limit value using the upperBound property of the ClassBreak class, and it is no longer possible to change the minimum value.
Although it is possible to manually rewrite the minimum value one by one, I would be happy if a property such as "MinimumValue" was added so that it can be rewritten in Python as before.