That argument would be more appropriate if OSM was about something other than where the streets went.
https://www.nytimes.com/1988/09/03/world/soviet-aide-admits-...
Detailed (<1:2500000) topographic maps were automatically classified as a state secret, and restricted on a "need to know" basis outside of the military until 1989.
A detailed article on this explaining how and why they went about it: http://www.hundzor.org/lj/10postnikov.pdf
'Where the streets go' is strategically valuable information.