There is no mandate that I'm aware of (not that I know everything about everything), but it's definitely the case that projects with "externalization potential"

There is no mandate that I'm aware of (not that I know everything about everything), but it's definitely the case that projects with "externalization potential" (making up a phrase out of thin air) will generally be more likely to get funded and prioritized (of course, why wouldn't they be preferred?). So, even without a mandate, the market forces at play in terms of proposing roadmap projects and choosing what to invest in, will naturally tend to favor those solutions with can pull double-duty (solve an immediate problem/pain-point that Amazon already has, and with a clear path/potential to be converted into or evolve into an external sell-able service too).