They tell the rank and file this to make them feel special. But in reality only the elders are regarded by the Watchtower society and legal authorities as "real" ministers.
When I worked in immigration, we were always exasperated when we'd get visa or passport applications which had been countersigned by a run-of-the-mill JW rather than an elder. Because when a passport or visa application is verified by a "minister of religion" we had to ring them up and check out their credentials with the head of their church such as The Catholic Church in England and Wales,or LDS Administrative Office etc etc. whatever the religion was.
Almost always we'd get someone claiming to be a minister of Jehovah's Witnesses and we'd have to tell them that they're not officially recognized as one even by their own church.
They were never pleased and would be adamant that we were wrong and we surely haven't been speaking to the right people because "the society wouldn't say that".