Since FMI version 2.0 we have methods: get_variable_unit() and get_variable_display_unit() that brings the information from the Modelica code for the FMU-module. What I can see there is no impact on what you obtain from get_variable_data() from the FUM-module on the results from a simulation.
Is there any python-package today that facilitate consistent handling of units in diagrams showing simulated data with JModelica, similar to what you get in for instance OpenModelica in the graphical user interface there?