Actually, the flow is a bit more complicated. There is a whole TV series, in 1984 and 1986 they selected two episodes per year to be projected as a double feature together with Nausicaä of the Valley of the Wind and The Castle in the Sky, then to celebrate the 40th anniversary of the TV series this year they stuck those four episodes together and renamed the resulting feature video Gekijōban anime Meitantei Holmes, where "gekijōban" is the usual formula used to address a feature, theatrical, real film and not just a selection of random materials. Hence, although being a montage movie made with old material, nonetheless it is a new movie.