Did you read the article? Because nowhere in the article does the phrase "due to water vapo(u)r" exist. In fact, they explicitly talk about why water vapor is prevalent and related to ice, and why subsurface ice scanning is so important (and is the only text I could find referencing vapor at all):

The need to look for subsurface ice arises because liquid water isn’t stable on the Martian surface: The atmosphere is so thin that water immediately vaporizes. There’s plenty of ice at the Martian poles – mostly made of water, although carbon dioxide, or dry ice, can be found as well – but those regions are too cold for astronauts (or robots) to survive for long.

They also talk about how NASA is not only aware of this but helping to fund the scanning technology that's being used to detect the subsurface ice. It's literally all in the article

It’s true that water is itself unstable because of the pressure or lack thereof, but I was always talking about water in its ice form my friend, you should read the article I linked from NASA, it’s super neat!