Do a more forward motion and flatter stroke. I am not sure how Korean coaches see and categorize looping. But in Chinese view, there is two main type of loops. The spin loop and the forward rushing loop. I think the name is pretty clear in of itself. The spin loop mostly for turning a heavy bottomspin into a topspin loop, this is a more upward brushing stroke. Forward rushing loop is for ball with less bottomspin or topspin, this is more a forward hitting stroke with brushing. Forward rushing loop is the preferred loop, only use the spinny loop if you can't do a forward rushing loop. Of course it is more difficult to pull it off, in China many non-formally trained player often complain about how they can't do a forward rushing loop on the internet.
Here is some video of Hong Kong player demo:
Listen to the difference in the sound.
Forward Rushing Loop:
Spinning Loop:
The more hitting you hit the louder the sound is, the faster the ball goes, and deeper the ball lands. The spin actually slightly stronger in forward rushing loops. Spinny loop are a more safe move, and have a larger window of timing since you can do it when the ball is falling. To reiterate, use forward rushing loop unless the bottomspin is too strong, the ball is past the highest point, or you want to be more safe.
There is a study of the spin of each stroke in small ball era. No speed gluing was used since the experiment was in 1987 and China's first speed glue user, Kong LingHui, started speedgluing in 1992.
In the study, spinny loop are called high loop and forward rushing loop are called forward driving loop. You can see forward driving loop is spinny on average and maximum.
http://www.ittf.com/ittf_science/SSCenter/docs/199208013- Wu - Table Tennis Spin.pdf
Edit: Technically, high loop (高吊弧圈球) is different than spinny loop(加轉弧圈球). High loop is even more spin oriented with a higher trajectory. Spinny loop is in between high loop and forward rushing loop. High loop is not used in game at all, high trajectory makes it a non-viable shot.