This reeks of propaganda.

Actually, if one has ever done any research about North Korea, the information in the OP is highly probable.  I was also able to find the same information (that North Korea is not repatriating the remains of its soldiers killed in the Russo-Ukranian war) from several other sources.  The reasons given for this is also highly plausible.  I've read reports, again from multiple sources, that for a long time North Korea sends citizens to Russia to work in demanding jobs, such as logging.  It is an important source of foreign exchange for them.  These workers are typically kept in guarded compounds and not allowed to mingle freely with others.

As an aside, the repatriation of dead soldiers from foreign battle fields was not usually practical until the availability of cargo aircraft, which began during WWII.  That is why there are 13 U.S. military cemeteries in Europe, mostly for soldiers killed during WWI.  I recall reading that during the Falklands war between Argentina and Great Britian in 1982, when Margaret Thatcher was the Prime Minister, there was a rowe over the British government's long-standing policy of not repatriating their war dead, but their plan to bury them in the Falklands.  I believe that eventually most of the 255 British casualties were brought back to England.

So 4,000 dead, and not a single POW.

"Oh, but we can't capture them because they're such savages, they blow themselves up rather than surrender!"

....riiiiight........



Or, "How conVEEEENient!"