Dead Men's Respite is not dragon tongue friendly because 1) Olaf One-Eye as a draugr has a single scripted line of dialogue in the common language of Tamriel ("Insolent bard! Die!") and 2) as a soul in Sovngarde he does not sally forth from the Hall of Valor to join the battle against Alduin. These facts could lend weight to the fraudster Olaf interpretation as described in the book
Olaf and the Dragon.
Korvanjund is the tomb of High King Borgas, a "chief supporter" of Prophet Marukh and the Alessian Doctrines (see
Pocket Guide to the Empire, 3rd Edition: Valenwood). The summaries of the
Five Songs of King Wulfharth seem to indicate that Borgas shunned the pantheon of his ancestors. Did he deny the gift of Kyne to his followers, viewing the Voice instead as a heresy against Akatosh? Well, whatever he may have thought, the draugr occupying the tomb with him won't be casually throwing around dragon language.
Ustengrav is the burial place of Jurgen Windcaller. Like-minded followers of the Way of the Voice presumably had the honor of being interred with him. They shouldn't be the type to take dragon-speech lightly (and the purpose of retrieving Jurgen's horn is to prove a dragonborn is worthy; death threats are discouraging and not appropriate for the task at hand).
