Thank you for contacting us regarding this observation. This is indeed an excellent question. I understand that you are looking for confirmation if it is indeed expected that iPads running iOS 13 present a desktop User-Agent. During one of the WWDC 2019 sessions earlier this year Apple outlined that these devices would use a desktop User-Agent to provide users with a desktop experience.
The same presentation, encouraged developers away from relying on this string to uniquely identify device types.
Introducing Desktop-class Browsing on iPad
“you should use feature detection instead of user agent sniffing.
In the past, some developers have wanted to know the user agent to specifically identify iPad, but our new desktop user agent on iPad will prevent you from doing this.”
If indeed the infrastructure is dependent on this user agent string, this will need to change as the device now presents the same string as macOS.