What are the other objections?
It’s not just that it implies faster-than-light communication, it’s that it implies communication at all.
Experiencing both bodies at the same time, you will be able to take actions in one body that you wouldn’t have done without the other one. It seems odd that with no biological changes to your brain, the mere existence of another similar brain changes how this one functions. Why would they be linked? This implies the observer is some external soul-like thing that can manipulate matter. If you can’t take actions based on your conscious experience, it implies the observer is dissociated from the brain and not created from it or able to interact with it.
I can definitely imagine a world where this is true, but it seems extremely unlikely based on what we currently know.
I played the game a few times when it first came out, I didn’t finish it and hadn’t played in years. This made me pretty familiar with the game in general, but not with some of the specific mechanics/interactions.
I started with the Tiny Pond level and afterwards did The River. For both the first plan that I executed worked, but for both this final plan was chosen only after scrapping many other plans that seemed promising at first, but in the end either my assigned success probability was too low to try them or important parts were missing/uncertain.
Usually for these kind of puzzles my first instinct is to explore around to figure out the rules, and then once I discover whatever interesting interaction the puzzle is based on, use that to solve it. I was surprised to find that even without doing any exploration, I was able to have multiple “aha!” moments during planning, where suddenly things clicked for a new way of approaching the problem. I think assigning probabilities to plans helped with this, as I could see when I think a plan only has a ~10% chance of working because some mechanic might work one way, but likely doesn’t, it helps push you to seek alternatives.
Another thing I noticed is I would often have the start of the plan and the end of the plan settled, but some transition steps in the middle unclear. I would spend a lot of the time trying to sort this middle out, but it turned out it was better to scrap these plans (as they weren’t possible) and go with an entirely different approach in these scenarios.