Neither R or T happen, so there is no "limited perspective" that could give you R or T if neither the events R or T ever happen at all.
If R or T never happen from an external perspective doesn’t really matter to us though.
If we accept many worlds as true for a second, then it follows that the total quantum states describes quite a lot, your exact configuration is somewhere within the total state. But crucially, your exact configuration is dependent on other configuration. At a large scale you depend on your parents having existed. So you can only perceive the parts of the total state where your parents existed, because any parts of the state where they didn’t exist does not contain a you to perceive. But this is also true for much smaller scales. From this, “collapse” is just your loss of vision into parts of the universe that you cannot be, and quantum uncertainties you can see is really just any quantum states that are not conflicting with your existence (where “you” is this very very specific configuration of you, so anything that alters your at all differently is in conflict with you) So sure, R might never happen if you want to say that, but R becomes what you can observe once you’re dependent on R, so it is reasonable to describe R as having happened from your perspective.
On your point about the lack of mathematical rigour to all this, I do not deny it, and am not well placed to resolve it, but just as how my arguments are mathematically unhelpful, I’m not entirely sure an actual mathematical solution would help much in a verbal discussion, as I suspect there would be a range of valid mathematical models which could be argued to line up with the range of philosophical interpretations, and without external observations we’d not be able to distinguish between them, but maybe that’s defeatist, we’ve gotten this far after all, maybe we’ll find a way to pin things down further.