“Without knowing what is in the reliquary, we can’t demonstrate anything.”
Yes, you most certainly can. You can demonstrate that what is observed in the reliquary can or can not be replicated using human blood.
Both of those eventualities have significant implications, and the publication of such a study might motivate the Church to allow testing.
“Yes, you most certainly can. You can demonstrate that what is observed in the reliquary can or can not be replicated using human blood.”
Not when a miracle is being claimed, you can’t.