This is why I have recommended the paper Hoffman has jointly co-authored on Eigenforms and Holography.
The answer, simply put, is that yes, objects do have the properties we perceive them to have because they are observer-dependent. Hoffman's layman level work leaves the causal, knowable nature of the world ambiguous and that to me sounds like Kantianism.
But this newer work makes some good headway on the metaphysical implications of ITP. I believe they say quite adamantly that there is no world sans observation, without observation/decoherence, we have the quantum state of indeterminate possibilities/properties. Upon observation, a classical state is registered:
" If interfaces encode information about fitness, then they do not encode information
about the observer-independent ontology or causal structure of the world. In the present
conceptual framework, of course, this is tautologous: there is no observer-independent
ontology or causal structure in any world that is defined only relative to an observer. "
As they continue, space just
is icons/eigenforms encoded into a 2D surface - where an icon's 3D appearance is encoded informational redundancy not only about an object's appearance,but possible actions one can take WRT to it. Apple can be eaten, thrown, smashed, juiced etd. "Space" is just how many bit-flips you need to get from one icon to another.
Objects in space are there to communicate information about your fitness. They are not apart from you - Yourself and the environment are co-dependent and co-arising. You're entangled. A system dividing itself into two -- but not separate things-- to communicate information to itself about how to perpetuate its own existence. If you don't interpret the icons properly, the Conscious Agent-Decision-Action loop breaks and both you and the environment "die".
So there is nothing "behind" or "underneath" appearances. Without observation, there is just superposition of quantum possibilities, but no "unknowable" world out there. I do believe, though, that there are many observers and many concomitant worlds, but these are
their worlds, so this might actually be a kind of ontological pluralism.