"Merge" option of the "Read Sequence"element works incorrectly

Here is the description of the "Mode" parameter of the "Read Sequence" workflow element:

Mode: If the file contains more than one sequence, Split mode sends them "as is" to the output, while Merge appends all the sequences and outputs the sole merged sequence.

But when I run a workflow: "Read Sequence > Write Sequence" with several input sequences and the "Mode" option set to "Merge", I get an alignment as the output.