Thanks for spotting this. Curly braces in LaTeX in string variables caused me a lot of headaches years ago, before we had "safe" strings. The routine to substitute variables into content areas would strip the first slash before a curly brace, so you'd have to put double slashes in the string in order to end up with \{. In fact, since you need to escape slashes in the JME code, this meant that you'd need four slashes! This was all so that the substitution routine doesn't interpret the curly braces as delimiting another substitution when the string was evaluated.
The 'safe' function works much better: it marks a string so that the substitution routine doesn't modify it, no matter when or where the string is evaluated. I've changed the substitution-into-content-area routine so it doesn't modify 'safe' strings, so now you get the same behaviour in the statement as for the choices, if the string is marked as 'safe'.