Would be interesting to know the thought process for doing this.
I refuse to use apps like this. None of my Apple IDs have payment information associated with them.
Even if it were just for iOS and iPadOS though, they do want iPad Pro to compete with desktops in places where expensive software runs. For instance, Grass Valley Livetouch could be done on an iPad.
It does seem like quite a reach but I think there are a few legitimate niche markets for that price point.
Comparatively, a high-profile client spending tens of thousands of dollars in ads isn't doing so on impulse, they're doing it cause it's their job. They'll open up a browser and punch in some banking details if it's the only way to get those ads out.