AWM is just a marketing puff to try and persuade that it may be somehow fundamentally different from PCM, it isn't. Technics introduced the first mass market PCM digital piano in 1986. For a time yamaha used sampled transients and fm envelopes to save on memory costs in the early days. Memory was expensive so all manufacturers have their proprietary methods of compressing the pcm wave to save on chip costs, and this also involves deciding where to divide up the quality... more on grand piano, or strings, or sax, whether stereo or mono, downsizing the bit rate or the sampling frequency etc, depending on their view of what their market wants in the sounds at that price point. But the object of the compression is to save money and the intended result is to restructure the pcm wave as close to the original recording as possible and thus keep its quality.
But the sounds remain all pcm - the same way that compact disks are recorded.