BQM 522

Can anybody explain ?  

I have seen it the first time in this game of Joanne Missingham (W) against Huang Xiangren ( http://igokisen.web.fc2.com/3qsh10.sgf)

The idea seems to be that Black at a ends weak, so playing there is not attractive. But how exactly? What is White going to do after Black a?

A thought...  

Tapir: sacrificing a stone may enable the hane at - but is it worth it? of course is not without aji while capturing it outright looks too slow. maybe i will try it if somebody comes around with the fancy two place jump instead of the second line hane.