With the new sounds introduced in 16w03a, there was a new chest open/close sound introduced. This sound was not applied to Ender Chests also, or if it was, it's no longer a working change.
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I'd say this is a feature request, as new sounds for the enderchest aren't introduced at all
migrated
merged with MC-91091
In sounds.json, chests use e.g. the block/chest/close variants whereas enderchest uses random/chestclosed (dunno what is intended)