The passage I bolded from what is to be 5.10.1's perlsyn answers my own question:
The behaviour of a smart match depends on what type of thing its arguments
are. The behaviour is determined by the following table: the first row
that applies determines the match behaviour (which is thus mostly
determined by the type of the right operand). Note that the smart match
implicitly dereferences any non-blessed hash or array ref, so the "Hash"
and "Array" entries apply in those cases. (For blessed references, the
"Object" entries apply.)
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