I think that's exactly what this is; it functions as insurance of sorts for the mobile world - such that they aren't totally locked out of a feasible platform (see tablets especially for both ) and also a "why not" for MS & Amazon both. It gives MS a starting point for an Android SDK + existing Amazon Android apps - and Amazon can bolster their offerings which currently are fairly barebones.

It could amount to little, of course. Even iOS apps on MacOS as a concept and practice has not remotely the luster ardent Apple acolytes predicted, certainly not yet even 7 months in.