Stop it with the tired lock metaphors, they are wildly inapplicable. If the WSJ wanted to require access to some secret knowledge or possession of some token for access, they could. Instead, they are dispatching on something the protocol they're using agrees you are free to set to whatever you want for the "best experience". In fact the specification specifically recognizes that you will change the agent. Much like the color of your car.

"If a user agent masquerades as a different user agent, recipients can assume that the user intentionally desires to see responses tailored for that identified user agent, even if they might not work as well for the actual user agent being used"

It's a param exactly equivalent to asking "who would you like to be treated as?" If I say "the pope!" and you respond by kissing my ring, I have not defrauded you.