I pretty sure in a warm climate this step could be eliminated, ensuring slips have new root growth before they are planted out gives them a head start.

That head start is required if you get some unfavourable temperatures. I have found following this method gives a very high success rate.

I have had only  five or six slips from several hundred not survive.

The harvested slips need a good chance in life, and placing them in 1 cm of water (warm) inside a coloured container is recommended. The  roots need to be dark and a clear container inhibits this root growth. I think this is why the toothpick method doesn't yield as high.

Place the container in a grow house on heat pads and under growlights. At 24 Degrees C it takes about 10 days for the roots to develop.

I tried adding a weak soution of liquid feeder  to the water, don't it madethe water go anerobic very quickly and the roots died. I recommend adding spring water or tap water leftin the sun for a few days.