Got it solved. I brought to the local Apple Store Genius Bar my 2018 iPad Pro, my 2015 MBP and a cable that I had at home (USB-c to USB 3). It did not work (witnessed by Genius guy). He brought one of the store MB Air used for customer support. As we connect the iPad, iTunes reacted with a "software update" (I did not allowed to update from the MBA)... So, no issues with the iPad and the cable... so my MBP was likely in need of a driver or "something". I rebooted my MBP and the 2018 iPad Pro. My iPad was already at iOS 12.1 and my MBP with all updates to Mojave and iTunes. I connected the iPad Pro and the MBP and after 3 minutes, iTunes gave me a message with "software update is required". After rebooting the iPad, it seems the update went to the iPad as it showed a classic firmware update progress bar. I also rebooted the MBP (so we ensure all updated were committed). After this process, everything worked as expected (restored from my iTunes backup).