The premise of your question doesn't work. If one person is going to learn about the option and a second one isn't, the better system for that to occur in is the one in which more people end up with correct behavior.

In this case, that means surprising the guy with existing (buggy) software; he'll have to fix the bugs. It means not bothering the guy who's starting a greenfield project. Neither of them will be subject to this bug.

The alternative, which you seem to be saying you prefer, is that the guy with buggy software should continue to have bugs, and the greenfield guy should also have bugs.