The old Promotor Fidei (devil's advocate) was solely responsible for arguing against the canonization of the proposed. It was his job to call witnesses from among the faithful and gather evidence of negative sanctity to ensure a thorough investigation. That position has been eliminated.
The Postulator who is appointed by the petitioner, normally presents the case only for the cause. Under the new law, he is responsible for arguing both for and against the cause. Now if you want to get someone canonized, are you going to present evidence to the contrary?
Opus Dei was therefore able to control the process and prevent those opposed to Escriva from testifying against him.
There is a Promotor of Justice who provides canonical counsel but his position is not that of the former devil's advocate. He is not required to gather evidence or call witnesses. His presence isn't even required.
Even if this was true, we have the dogmatic fact of St. Josemaria's canonization to prove that these witnesses were either lying or sadly mistaken.
I want to see the evidence that the so-called "devil's advocate" was an official of the Roman Curia from ~1000-1500.