Filter on binary uploads is inconsistent

Upload a new file (style.css, see attachment), no problem.
Click on the new asset, click edit. Upload the same file or an "updated" version: exception: Invalid extension css. Valid extensions are png, jpeg, jpg, gif, pdf, doc, xls.
Why is there a restriction at all and can it be removed?

Workaround: upload a new binary from the updated file and delete the old one. This will break existing references.