You're certainly right if the language is intended to be taken with that degree of precision. But how could a Satanist confect the Eucharist, since he would not have valid orders? Unless, of course, the Satanist is, God forbid, also a Catholic priest. Or, God also forbid, if a Catholic priest who is not a Satanist nevertheless performs the consecration, intending that it be used sacrilegiously.
I surmised therefore that it referred to theft, since that is sometimes given as a reason for having someone always present during Eucharistic exposition or adoration, such as the 40-hours devotion.
I plead ignorance as to the details of the Black "Mass". Do you have any further information?