Cant destroy evidence if you stop the war from happening. Russian saboteurs were captured. Many were in plain clothes and no dog tags. But luckily, they had their government issued military ID. I mean they're 1 step from being treated as a spy. Which can carry the death penalty. Something in the Geneva Conventions about being able to ID a soldier compared to a spy. Uniform, rank, dog tags, military ID, etc...
Which is why in WW2, many captured airmen who were being smuggled out of the hostile territory by the resistance didn't want to give up their dog tags. They were in civilian clothes and that was the only item that ID'd them as an airman and not a spy. Which the Ghestapo would have shot. The down side to keeping the tags are that instead of hiding as a civilian, it ID's them as a soldier.