When connecting to SSAS Tabular through a gateway the data model in Power BI desktop will automatically inherit the data types and formatting of the calculated measures. This is perfectly fine for 90 percent of the reports one wants to generate. But sometimes you need to change the formats of the measures (in a report you want to change from the standard thousands point (economic value) to only show the value in whole thousands. And by the way - when you want to export the table/diagram with the values (say to Excel) it should export the real values (with all the decimals) rather than export the formatted value that cut the decimals.
We want of course to set the formatting in the SSAS Tabular model - however it should be possible in the special occasions to change the formatting directly in the reports that is connected to the SSAS Tabular.