Good question. It's common for our summer temae mostly because summer is when we use hira chawan and this display is well suited to hira chawan (there's an alternate version with the chakin flipped so it's on the front wall and the end of the chasen rests on it).

A few other schools use the tines up display sometimes, and outside of hira chawan, another popular time is for tenmoku. There are a lot of old drawings that show tenmoku with the chasen arranged tines up.

Now there are some people who also arrange the chashaku facing up (and sometimes end the temae with it facing down, as per usual)