Took a feature class and made a table view from its attribute table, using Make Table View. Tried to use that table view as input to Append, to append to a table. Failed with Error 000573: The input and output must both be of the same type.
Why didn't this work? If it should not work for some reason (it looks as if it should), why did the Append tool let me try to run instead of flagging the error?
Try writing the table out using CopyRows and then doing the Append.
Help for Append mentions that: "Input datasets can be point, line, or polygon feature classes, tables, rasters, raster catalogs, annotation feature classes, or dimensions feature classes." It does not mention transitory entities like Table Views or Layers.
This is a known issue with both the Append (management) and Merge (management) tools, which we will attempt to address as soon as possible -- you can follow the issue by using the identifier NIM081084. Both tools support table views and feature layers, but the bug prevents a table view made from a feature class from being appended or merged with a table. You can append or merge a table view made from a table with another table.
For the time being, the recommendation above to copy your table view to a temporary table using the Copy Rows (management) tool is the best solution. You can even copy to the in_memory workspace so that you don't have to consider cleaning up this intermediate data.