iOS: Id set using Flex library not recognized by Appium

Hi,

our iOS devs are using Flex library https://github.com/Flipboard/FLEX to set-up id on element but we are having trouble to run scenario using this id; it seems tha Appium is not able to see them, what is confirmed by using Appium desktop inspector: this id are not displayed in the inspector.

Do you know if Appium support this library?
If yes, what can cause our issue here?

Appium version: 1.9.1
Appium desktop version: 1.14.0
xcode: 10.1

Thank you in advance