PivotTables are undergoing a major revision in build 15.41 of Excel for Mac, which you can get right now.
Go to the Help menu in Excel and choose Check for Updates, which launches AutoUpdate app.
In AutoUpdate, click the check box to join Insider, and leave the setting at Insider Slow. This will give you next week's general release of build 15.41 a week early. The new build should have the same code in it as Excel for Windows. If there is still a difference, there is likely a problem on the PC side.