Vos Savant mentions this, and she's kept track of who did and didn't understand the conditions:

> And a very small percentage of readers feel convinced that the furor is resulting from people not realizing that the host is opening a losing door on purpose. (But they haven’t read my mail! The great majority of people understand the conditions perfectly.)

https://web.archive.org/web/20181118225305/http://marilynvos...