You're right, DJI should mention this clearly within the manual.
The problem is, that you don't have full control over all three axis and throttle as is required for safe operation in Atti mode and supported by RC3. The idea behind the motion...
Most likely "don't do that".
VPS sensors will be the first thing that confirm successful ascent, if you block them then it'll have to rely on the slow feedback from other sensors.
My guess is it's the combination of not having a working downward...
The Avata 2 cannot be controlled in Atti mode by the Motion Controller. And in this case there was a quite dark room and no GPS, so the Avata went into Atti mode. I avoid flying both my Avata 2 and Neo indoors with using the Motion Controller and...