shorthand for applying an expression to each item in a list

If you used "sequence" instead of "list" and wanted a short description
for the XPath 3.1 map operator "!" I could easily agree with that. But
xsl:for-each with a sequence constructor and potential xsl:sort key
declarations seems a bit oversimplified with your description.

And let's not forget that XSLT is declarative so any evaluation giving
the prescribed result sequence is allowed.