Yep, and the same goes for Amplitube which also has no real concrete information on what input levels to use for an accurate response. We're in 2023 and they still want us to guess this stuff (despite IK advertising accurate gain levels as a defining feature of their products).
This is what IK advises but everyone is using different pickups, hits the strings with a different ideas of what picking hard is and have pickups at all kinds of distances. I can just about clip a 14dBu input, but for some people 7dBu (or less) is fine. 12dBu seems to be a good ballpark for IK's levels, aside from the fact that some of their own devices have a value of -6dBu. It works well for individual setups and can result in pretty accurately gain matched models, but as soon as someone else tries them it goes out the window. Measuring and providing numbers gives repeatability and consistency for everyone.
I stumbled on this thread with some contributions from
@yeky83 talking about the incredibly weak reamp signal level - how he managed to remain calm when dealing with such a condescending tone from others in there is beyond me. He was the only one talking in facts, using specified values and backing up what he was saying. Absolutely staggering way to be talked to from a company representative.
https://gearspace.com/board/product-alerts-older-than-2-months/1246236-ik-multimedia-unveils-axe-i-o-premium-audio-interface-7.html