Hoping I might be missing something here.
In ArcMap, when symbolising a raster with a stretched renderer, you could edit the High/Low values as so:
I cannot spot this in ArcGIS Pro?
I don't have access to ArcGIS Pro now.
In the screenshot, the Stretch-Type in ArcGIS Pro is "Standard Deviation".
What happens if you change the Stretch Type to "Minimum-Maximum"? Are you not able to edit the values under Color Ramp?
Sorry, should have had that enabled in my screenshot for consistency.
However, makes no difference.
Under the statistics drop down change the option to "Custom". This will enable you to set the mix-max at the bottom of the symbology pane, which is usually greyed out. It's still a bit odd though because the minimum value doesn't update as it should but the symbology still applies in the map.
Retrieving data ...