Seems to be a good approximation! Dividing into 3 caregories (spi/internal/public) semm to be very simple and clear! But, as you mentioned, "Grouping code into packages in this manner is an ongoing process and is still incomplete. The reason we could not do it en masse is, oddly, backwards compatibility."

Maybe, it makes sense to create a more strong criteria? Class/package list, for example.