Tabular models store data in a highly compressed form and sometimes this has unexpected consequences. In what I encountered today, we had a column which was input by users. Since this was test data, it had all sorts of nonsense with values like:
aaa
AAA
aAA
The tabular model looks at this through the lens of collation. In the instance of case insensitive models, all three values are considered the same and only one value will be stored. In fact, the first value it encountered will be the winner. So the only output from the model was "aaa."
I can't imagine this is a big issue - I mean case sensitive data models are a nightmare. But it's definitely something to be aware of.
Here's more on that:
https://docs.microsoft.com/en-us/sql/analysis-services/tabular-models/table-properties-ssas-tabular?view=sql-server-2017