I think a good approach to answering your question, is to make a timeline of quantization, then things get more clear for you.
(Don't know the year): Boltzmann considers quantized energy levels for deriving his distribution.
1900: Planck proposed a frequency distribution for black body radiation in agreement with experimental data. He then showed that if the energy content of the oscillators in the black body is assumed to be quantized, his distribution will follow.
1905: Einstein applied the notion of light quanta to the problem of photoelectric effect leading to a satisfactory explanation which proved such a notion to be close to reality.
1913: Bohr proposed his atomic model inspired by Einstein's and Placnk's ideas.
1915: Sommerfeld (and maybe others too) generalized Bohr's model and proposed a mathematical quantization rule.
There is of course much more than that to the history of quantum theory but these are the starting points of quantization. So it was started as a good postulate that could produce results in agreement with experiment.
But then Heisenberg and Schrödinger proposed their theories.
I think Heisenberg also postulated quantization rather than deriving it, I'm not sure. But Schrödinger did derive quantization from his wave mechanics. Quantization is mainly because of the restrictions made by boundary conditions. That's how it arises mathematically. I don't know if there is an explanation in terms of physical principals.
But other formulations of QM also give rise to quantization so I can't say yes as your answer.
I think we always talk about the wave nature of particles because wave mechanics is the most popular formulation of QM otherwise other formulations don't suggest such an interpretation, at least not explicitly.
So I can only say that Quantization is a consequence of Quantum Mechanics.
