If you keep the encrypted passwords in one "secure" place and the honeychecker in another "secure" place, then the system is secure unless both systems are compromised.
A. It doesn't do a lot to 'secure' the password credentials (in the way most people think of the term). It just tells you that someone tried to login with a honeywords. What happens then is a difficult process.
B. It's only belt-and-suspenders redundant to the extent the difficulty of cracking the honeychecker server is independent of the regular login server. It's certainly beneficial that it has a much simpler API, but if your honeychecker is just a different Ruby Gem hosted on a different Linode (for example) the benefit are lessened.
It's classic engineering redundancy.