Without a function that allows an external package to construct a Manifest with arbitrary values (including ones for this value), I think I'd prefer to leave these properties exported.

Also, rather than these individual PRs, can we have that discussion about an export policy (in an issue dedicated to it)? It seems clear you have some guiding principles you're operating by, and it would be good to make this explicit.

That's an accurate functional statement, of course. But as a policy, it addresses only one of the relevant factors - minimizing surface area. On its own, we'd rapidly reach the point where we export nothing at all. The question that we need to answer is what we want the surface area to be, and how that relates to a release process.

I could certainly be convinced that the right position for now is to be conservative and export absolutely nothing publicly. But I want us to set a goal, even a loose one, and move towards it, rather than iterating without a plan.

Closing this - to the extent we've articulated a policy, it does include exporting Manifest.