Trafficking covers false pretences as well as the physical movement. I don't think any of the girls are physically forced to Hong Kong, but I do believe that many of them genuinely believe that they are coming to be dancers (the official version) not prostitutes (the reality). Whether that is true in this case I don't know, obviously, but I do know of others.
Another sickening example that I learnt of recently is that one of the "recruiters" based in The Philippines (by the name of Sally) recently trafficked her own daughter to work in one of the bars in Lockhart Road (in the chain owned by Cynthia, the uber-mamasan, who should be locked away for a very long time).