This is the usual way to leave the platform before performing a half turn, since you only need to change one hand after turning. Some people turn with both hands in a normal grip and then move both.

Put your right hands on the bar so that your hand is underneath the bar and your palm upwards. Put your left hands to the left of your right hand with a normal grip.

These notes are provided ONLY as an explanation of the trick.
If you want to perform it yourself - get an expert to teach you.