Ok, looking at my own question, I noticed what was going on.
The longitude -122.44919479999999 is somehow bugging Tableau. Using ROUND() fix the issue.
It does look like a bug
When using Split from the field context menu -- it will automatically truncate the lat/lon values to look like this:
I am not able to reproduce the defect you are describing. Can you share the exact steps or a screen shot that includes the data pane and numeric properties of the split lat/lon fields?