Superposition isn't particularly hand-wavy. It's the basis of various technologies, and of precise numerical models we use to build technologies.
Quantum collapse is hand-wavy, and that's because it is not well understood. It might not exist (in which case superposition of mind-states is a thing), or it might exist (in which case mind-states may be definite). Quantum mechanics that we can calculate doesn't give an answer either way, even though it gives lots of other answers very precisely and correctly.
> Wiger doesn't know about it, [...] just seems like silly mind games.
When only applied to a single measurement it does seem like silly mind games, you're not wrong.
The motivation for those thought experiments was to try to reason back from the consequences found from more complex behaviour observed with multiple measurements, back to a simple system with only one measurement.
But when you have many measurements with entanglement, of which there are numerous physical experiements and confirmations by now, the idea that there are just multiple, correlated probabilistic states ready to be observed that we're not yet aware of is not consistent with physically measured behaviours. Those measurements aren't hand-waving, they are hard data, even though my explanation here is hand-waving and doesn't go into it.
> I side with Einstein with his view that everything is already in one state or the other
Numerous experimental results now contradict this view, or require other strange things to be true about the world (for example superdeterminism was mentioned in the article).
Actually, it is Bell's Theorem / Inequality and related experiments that are relevant here. https://en.wikipedia.org/wiki/Bell%27s_theorem
These experiments were really the nail in the coffin for Einstein's position for most physicists. Having to admit non-local hidden variables is a pretty distasteful result.
An observer changing the outcome is a very real repeatable experiment with non wavey results.
https://physicsworld.com/a/do-atoms-going-through-a-double-s...
It's similar to the problem that has been highlighted here by OP, to quote the artical I posted
"Indeed, the results of both Truscott and Aspect’s experiments shows that a particle’s wave or particle nature is most likely undefined until a measurement is made. The other less likely option would be that of backward causation – that the particle somehow has information from the future – but this involves sending a message faster than light, which is forbidden by the rules of relativity. "
> "From the point of view of the friend, the measurement result was determined long before Wigner had asked about it, and the state of the physical system has already collapsed. When now exactly did the collapse occur? Was it when the friend had finished their measurement, or when the information of its result entered Wigner's consciousness?"
This to me, shows just how hand-wavy the whole superposition/quantum collapse stuff really is. I have to say I side with Einstein with his view that everything is already in one state or the other. We don't cause the system to choose a state when we measure it. We simply discover the state it was already in. It is one thing to assign a probability to which state we will find it in. It is quite another to create an entire theory around quantum measurement.
There is nothing mysterious about this paradox. The friend performs the measurement ans discovers the state of the particle/system. Wiger doesn't know about it, but that doesn't mean it's not in that state, he just isn't aware of it yet. The fact this is a paradox just seems like silly mind games.