If you're not a HKID holder, which I'm guessing your aren't because of the ability to do the TT course. You will not be given a start until there is not 1 person available to do the ab-initio course. If they are finding 1 person per month to do ab-initio you will continue to have you're course deferred. It is the Immigration Law, not CXs desire.
They are still finding plenty for the ab-initio courses.
Not stringing you along? I think you will find that is exactly what they are doing, only with a longer piece of string.
Every course that starts before you, puts you further down the seniority list.
I would be getting out there and trying to get a real flying job, remember although you may have passed the interview process, your start, when/if it comes is not in any sort of order, it is who they think will fit the position best.
If you've sat on your arse for the last 18 months, you wouldn't be my first pick.