David Wallace

That is a very strong counter argument, and it aligns with what philosopher Daniel Dennett called the intentional stance.

David Wallace, one of the thinkers in the sources, champions this exact view.

Wallace brings up playing chess with an AI, right?

He does.

There are, in other words, beings identical to me at the time of splitting in these other worlds and all of us came from the same source which is me right now.

Philosopher David Wallace pries open this view a little deeper, arguing that the sense of I can only make sense if identity is confined to a single branch of the quantum multiverse.

Since it's not clear how this can happen, Wallace concludes that we may have inadvertently demonstrated that many worlds is not a conceit of multiple selves, but rather it is dismantling the entire notion of selfhood.

It denies any real meaning to you.

It also makes direct confirmation difficult.

Modern defenders such as David Wallace argue that worlds are not fundamental objects with sharp borders.

They are emergent patterns, much as many useful physical categories are emergent rather than written into the deepest equations.

A branch is an approximately autonomous quasi-classical structure identified through decoherence.

The argument was not that an observer is uncertain whether outcomes will exist.

The observer can be uncertain which future branch they will find themselves in, and a rational agent under specified principles should make decisions as if outcomes are weighted by squared amplitude.

David Wallace refined this program.

Other philosophers and physicists developed related ideas involving self-locating uncertainty and the structure of rational expectation in branching situations.