Agreed. That membrane alone would be nearly impossible to make a consistent membrane that behaves identically while also expecting it to face identical circumstances entirely, even once. Maybe once in a lab it’s possible.
Differences in temperature, viscosity of fluids, gravity in one’s location, levels of light (photons hitting it)… magnetic fields… _so many_ and THEN you that that complexity exponentially increased by the number of interacting cells and their unique relationships between them.
Impossible? No, but extraordinarily difficult in a real world situation.
Even in alternate universe scenarios, a single breath can change everything between two universes if a single factor is different.
Look at the different inhaling a single molecule of oxygen can make.
The bond breaks. One O goes to one molecule, the other to another. How can you determine which molecule it bonds to when there’s millions of oxygen molecules per breath (and most of them not oxygen at all, but polluted in other ways.. the body makes do with what it gets.