Despite having had IDC before and being a current member in another country they asked me for a 15k bank guarantee when I approached them last week.

I find the benefits of the HK Plat charge card are lacking and the fee is the same. Tried to global transfer to IDC: Cannot. They told me to apply and mention my HK card in the relevant field and they will see stuff. They told me to cancel my HK card once they have issued my IDC.

4 days later they contact me to say they have received all my documents and oh by the way, we need a bank guarantee for 15k in order to go ahead with this.

This is definitely a new thing. I had IDC before and there was no such thing. My country of residence now is different (and considered higher risk) to back then so maybe that's got something to do with it.