Yes, the web map JSON always contains 255 for the outline opacity. Here is a sample:
....
"symbol":{"color":[255,0,0,115],"outline":{"color":[255,0,0,255],"width":1.5,"type":"esriSLS","style":"esriSLSSolid"},"type":"esriSFS","style":"esriSFSSolid"}}]}}]}}],"exportOptions":{"outputSize":[804,724],"dpi":96}}
Where as the value of a for the polygon outline is correct (ex. 0.1) when the call to the PrintTask.execute is made.