Look at the language of the UNSC Resolutions that India and Pakistan committed to implement - specifically the part that states. If the UN did not consider J&K disputed territory, why would it talk about a plebiscite to determine the question of accession of J&K to India or Pakistan?
"... Noting with satisfaction that both India and Pakistan desire that the question of the accession of Jammu and Kashmir to India or Pakistan should be decided through the democratic method of a free and impartial plebiscite ..."
"... and to create proper conditions for a free and impartial plebiscite to decide whether the State of Jammu and Kashmir is to accede to India or Pakistan."