Somehow I had forgotten the difference-in-degree-only distinction between subjectivity and objectivity that you stated. Okay! Makes sense.

But I'm still not sure you're saying anything beyond that which I agree with.

Babies learn object permanence--that if a ball goes behind a chair and comes back out, it's the same ball! (This is an extension of the concept of object identity.) So since babies learn to understand that balls don't just spring into existence and disappear, but rather exist...they are...subjective? Whereas if they just accepted the sense-data they were exposed to without understanding this..."ball! no ball!" ball!" they would be more objective? Isn't this a very strange way to use the word?

You rely on object permanence all the time. For instance, I presume you have a car. It is your car and it is the same car every time you come to it. How is it useful to say that understanding that the object the-car-that-is-yours continues to exist while you're away from it is in any way "subjective"?

Instead, it seems to me that "objectivity" is built out of understanding. You understand that this thing is-the-case-regardless-of-perspective, and because this thing is, so is that--on and on, building up onto the shoulders of giants. That's kind of the point.

It's also true that because we can be mistaken therefore objectivity cannot be absolute: we might not realize that we are taking a perspective-dependent view when we believe we're taking a perspective-invariant one. But understanding is how we get there, it seems to me--and you place it on the wrong side of the ledger!