Happy New Year!!
First of all, it is definitely a good news that they have started your BCG. You are 99% progress to dm now!!! Please do not worry about the BCG time frame, I have heard HK office usually takes longer BCG time than other Visa office this year and it is totally normal for HK applicants, there are several applicants are in the same situation as you right now. All you need is to wait patiently right now and good news will come, if you really worry about it, feel free to order the GCMS note. Just keep in mind, it takes 1 month to receive your GCMS note after you order it, you might get your DM in next several weeks hopefully. At this point, you might not need GCMS notes, since it is already very close to the end of journey. Have a nice day.