rv2av doesn't seem to care whether it gets an array reference or an array.

Update: This is confirmed by BrowserUK's less specific test and by looking at the 5.8.8 source:

PP(pp_rv2av)
{
    ...
    if (SvROK(sv)) {
        ...
        av = (AV*)SvRV(sv);
        ...
    }
    else {
        if (SvTYPE(sv) == SVt_PVAV) {
            av = (AV*)sv;
            ...
        }
        ...
    }
    ...

    ...return something derived from av...
}
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