When you use collect to pull a view from HANA DB it does not properly read the column data type definitions to create the destination table so all columns are created at NVARCHAR(255).
Additionally the System Type Model does not properly pick up the columns that make up a view so there is nothing in the model to define what it should be.
As we do more with ABAP CDS (which present in HANA as a standard view) and with CDS views in HANA this will become a larger problem.