The Reclassify Tool in ArcGIS Pro is limited compared to ArcMap.
First, there is only one automatic method (Equal Interval). You can get a couple other techniques using the "Slice" tool.
Secondly, you don't see the histogram of the raster data. This is powerful information!
The two best courses of action right now are:
1) Use ArcMap for this process (you get to see the histogram to make an informed decision)
2) Follow the below procedure provided by the Dev team:
- Add your image to the map
- Symbolize it with your desired classification method
- Open the reclassify tool
- Add image to tool and it will take the values from the renderer
Please improve the tool to function more like the one in ArcMap.