1st, I correct my line. "..which other priests do do have" should be "..which other priests do not have".
You wrote: "Some good advice and preventive medicine can aldo be given by priests". Ah, but that is Reconciliation! I deliberately used the older term Confession as that would be Opus Dei's understanding of the Sacrament.
The average person is not going to look up linkin or whatever to find out the affiliation of a priest making comments who doesn't have any initials after his name. They assume he is a Diocesan priest. An example: Father John Flader who was born in Wisconsin, trained in Rome, and since 2009 has had a column in the Archdiocesan newspaper of Cardinal Pell's former seat, Sydney NSW. He never identifies himself as Opus Dei apart from his online bio.
Opus Dei hides behind numerous fig leaves in its activities, and you have to ask why. It is "affiliated" with several schools such as The Willows and Northridge (Illinois), and Tangara and Redfield (NSW). Affiliated? Ha ha!