Well, the release of missing episodes on home media is a function of BBC Worldwide, which is
a money-making enterprise. More to the point, we're talking about the hardcore fans of a television show. The relationship to any public good is so distant that "responsible" and "irresponsible" don't really enter into it. Some fans are really worked up and want the BBC to undo the confusion in their minds. Well, that happens with the new series every year, when people want to know what's been commissioned, what's the schedule, where are the trailers, etc. But that doesn't make it irresponsible of the BBC not to time its announcements to those few hundred people.