As in the title. The test tests fn:current inside xsl:evaluate, but per the section on the static context, that function is not allowed in dynamic evaluations:

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Function signatures: All core functions; constructor functions for named simple types included in the in-scope schema definitions; all user-defined functions and accumulator functions present in the containing package provided their visibility is not hidden or private; and an implementation-defined set of extension functions.

Note that this set deliberately excludes XSLT-defined functions in the standard function namespace including for example, key, current-group, and system-property A list of these functions is in G List of XSLT-defined functions.
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