I don't dispute that they all had feathers in.
'Filled' on the other hand, is moot.
Many of the doss bags I saw/used back in the day (having been frequently used and subsequently laundered), if held up against the light would display very clearly that the once-fluffy down had lost 99% of its natural oils, and with them its 'loft', so - instead of filling the individual quilted pockets as they might have on leaving the factory, the sad tattered remnants could be seen sitting in tiny piles in a corner of each pocket, tumbling from one corner to the next if the fabric was rotated.
Hence my observation ( a looong way upthread) about the inadquacy of the design criteria when they were first introduced.