Turned out that the phrase "Plan B" has a special connotation in the US (a day-after contraception pill), which I wasn't aware before . One of the US-based devs pointed this out and we're discussing how/if to change the option name and to what alternative (needless to say some users didn't like the "paranoid" name either):
https://t.co/0YBigxAH0V

I guess Qubes OS is getting ever more mainstream... :)