Saxon

I thought any (experimental) XPath 4.0, XQuery 4.0 and XSLT 4.0 support is restricted to PE and EE but somehow I find that both Saxon HE 11.5 and 12.2 from the command line execute XQuery 4.0 code using the -> compact function syntax just fine e.g.

xquery version "4.0";

for-each-pair((1 to 5), (1 to 5) => reverse(), ->($a, $b) {$a + $b})

PS C:\Users\marti\OneDrive\Documents\XQuery\XQuery4\thin-arrow-operator> type .\thin-arrow-function1.xq
xquery version "4.0";

for-each-pair((1 to 5), (1 to 5) => reverse(), ->($a, $b) {$a + $b})
PS C:\Users\marti\OneDrive\Documents\XQuery\XQuery4\thin-arrow-operator> java -cp 'C:\Program Files\Saxonica\SaxonHE11-5J\saxon-he-11.5.jar' net.sf.saxon.Query -t thin-arrow-function1.xq
SaxonJ-HE 11.5 from Saxonica
Java version 1.8.0_372
Analyzing query from thin-arrow-function1.xq
Analysis time: 343.6697 milliseconds
<?xml version="1.0" encoding="UTF-8"?>6 6 6 6 6Execution time: 29.0722ms
Memory used: 50Mb
PS C:\Users\marti\OneDrive\Documents\XQuery\XQuery4\thin-arrow-operator> java -cp 'C:\Program Files\Saxonica\SaxonHE12-2J\saxon-he-12.2.jar' net.sf.saxon.Query -t thin-arrow-function1.xq
SaxonJ-HE 12.2 from Saxonica
Java version 1.8.0_372
Analyzing query from thin-arrow-function1.xq
Analysis time: 342.058 milliseconds
<?xml version="1.0" encoding="UTF-8"?>6 6 6 6 6Execution time: 48.3746ms
Memory used: 53Mb

Undocumented or unintended?