null stylesheet?

My apologies if this already appears in the archives or is already a
known issue. Note: this is a very non-urgent issue, asked for the
sake of completeness and curiosity. 

For various (slightly embarrassing) reasons I'd like a placeholder
dummy XSLT 1.0 program. I initially wrote

  <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
    <xsl:template match="/"/>
  </xsl:stylesheet>

and that works perfectly well. But then I tried the slightly simpler

  <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0"/>

I think that is allowed by the 1.0 spec: ".. stylesheets may contain
zero or more of each of these [top-level] elements". But I'm far from
certain. In any case, most processors I have easy access to[1] are
fine with it. But Saxon-HE 9.5.1.3J run from the commandline
complains that "The supplied file does not appear to be a stylesheet"
(this is an error, not a warning; # XTSE0150).

So ... what's supposed to happen? And if Saxon-HE 9.5 complains from
the commandline, why does it not complain when run inside oXygen? (Is
oXygen intercepting that message? Or perhaps oXygen is generating the
message, and I just don't know where to look for such errors?)

Notes
-----
[1] 1. xsltproc "Using libxml 20708, libxslt 10126 and libexslt 815"
    2. Saxon 6.5.5 via oXygen 15.2
    3. Xalan via oXygen 15.2
    4. Saxon-HE 9.5.1.3 via oXygen 15.2
    5. Saxon-PE 9.5.1.3 via oXygen 15.2
    6. Saxon-EE 9.5.1.3 via oXygen 15.2