You are right. It works that way on my USB OTG wired
Gamesir T1 controller. Pushing right stick take picture /video and pushing left one switch mode video / photo.
By the way, lately I noticed aTelloPilot app photo mode hanged after switching from video mode and taking some photos. Controller sticks still alive but photo button neverending blinks and you can't shoot photos anymore until landing.
Sometimes it happend to me after taking a dozen of photos and other times only after a couple of them.
It's very annoying. Has it happened to someone else ?