Actually, Korean military had an experimental VDI program years ago, but the program failed mainly because of the price, most of which had to be spent on Windows license. IIRC, after creating a small prototype, the program is eventually scrapped.
So, no, this is not a negotiating move. Also, I believe this will definitely happen, because Windows 10 is stupidly expensive.
The official announcement from Korean government (Korean): https://www.mois.go.kr/frt/bbs/type010/commonSelectBoardArti...