It seems to me that "pastor" or "shepherd" implies a flock. If someone says, "I'm a pastor," a legitimate response is, "Whose pastor are you?" And if you are not anybody's pastor you might still in a sense be a pastor who is between jobs, taking a sabbatical, on leave or whatever. But you don't remain a pastor to everybody in the church/denomination in a general sort of sense.
I think Richard Neuhaus had this debate with the ELCA as well. He took Charles's position, which is also close to the Catholic position, that one is or can be a pastor for the church at large. But his ELCA bishop in New York took the position that one must be working (or seeking work) at least part time in a parish or institution related to the denomination in order to remain on the clergy roster over a long period of time. Thus, he warned that running First Things and doing the other things Neuhaus was involved in did not amount to doing enough "pastor stuff" to merit remaining on the clergy roster.
Ironically, once he was a priest Neuhaus gladly accepted parish ministry as part of his duties as prescribed by his Catholic bishop.
Of course Lutheran ambiguity about ministry is nothing new, and applies to all Lutheran bodies.
The situation today, however, is that there is different
usage common in various bodies. In the LCMS, the ordinary usage dictates that "pastor" refer only to someone in a specifically pastoral ministry. The LCMS style book says: "pastor — May be used as a title for a clergyman, but should be limited to ministers who lead congregations."
In the ELCA, on the other hand, the term is typically used as synonymous with "member of the clergy," whether that person is currently in a specifically pastoral call or not. The ELCA style book says: "clergy
as distinct from laity; use also 'pastor,' 'members of the clergy,' 'ordained minister.'"
One can argue about usage, but it doesn't seem very productive to do so; sort of like arguing with a Canadian about whether one should write "honor" or "honour." It's just a different
usage in a different context. The important thing is to understand the difference, respect the difference, and not argue that one is right and the other wrong.