I don’t think there’s a compelling exegetical reason in this particular case to interpret earlier events by the later…

Well, you’ve also got the development of the creation narrative to take into account, the general disintegration of human experience: expulsion from the garden, death and pain, violence, the express rejection of divine purpose. Moreover, there is the literary-historical argument that Genesis 1 is the product of a Deuteronomic theology, is there not?

…your “microcosmic” reading denies full human status to everyone who isn’t part of the Abraham-Israel-Church microcosm.

Not at all. The argument is that God brought into existence a new humanity - not a superior humanity - in the midst of the old humanity. What made it different, at least in theory, was a) the presence of the living God in the midst of Israel; and b) the obedience of Israel to the Law of God. You have missed my point somewhat if you understand it as an ontological distinction. It is not even, necessarily, a moral distinction. Israel was not chosen for the sake of ethical or political or cultural superiority but for the sake of faithfulness to the creator God.

Why not just let the Abrahamic covenant supplement rather than restate that original fulfilled blessing?

Because not only the creation narrative but also much of Old Testament theology appear to suggest that something of the character of blessing was lost when the couple were expelled from the garden. Again, this is not about being fully human - it is about being a sign of how God intended humanity to exist in intimate and obedient relation with its creator. At the very least, the Old Testament regards the nations are seriously misguided for their worship of idols. Israel never believed that it was meant to supplement that condition - it was an alternative to it.