Formatting removes xml-stylesheet processing instruction attributes

[catfacetaro]

When formatting document with the xml-stylesheet processing instruction,
it removes all attributes, except version and encoding.

Example:
<?xml-stylesheet href="my-style.css" type="text/css"?>
becomes
<?xml-stylesheet?>

However,
<?xml-stylesheet href="my-style.css" encoding="UTF-8" type="text/css"?>
becomes
<?xml-stylesheet encoding="UTF-8"?>

It seems like it treats the processing instruction xml-stylesheet like xml.
The xml-stylesheet does not have attributes encoding or version, but it has attribute href and type.