Tan Tui arm out?

Just curious, what is the purpose of the arm being held out to the side in Tan Tui?

Shaolin based forms are new to me and not sure the purpose.

Thanks!

I'm guessing but I'd say you look at xiao hong fist for the start to an answer.
https://www.youtube.com/watch?v=MD4zJv-rwLM

and this one:
https://www.youtube.com/watch?v=RciA1j1uPek&t=10s (around the 6 min mark)

two different perspectives on it I'm sure you can find more.

Thanks! I figured it was for something, but just didn't know for what.

Yanlei and YanZi both use it as a stretch as well for warmup's.
Start in horse stance and shift to a bow and arrow stance with the arms out as in Tan Tui and really reach extending the shoulder of the arm straight ahead.
Reaching 3-4 times then switch to the other direction and repeat.

So that could be a part of why it's in that set as well.

The set obviously is all about the mabu - gongbu transition.