This is why I require all my software to have bespoke compilers otherwise how can I trust the devs know what their code is actually running!?
In old days we chose between Turbo/Borland C, Quick C and GCC. We didn't think them same or trust blindly even if we didn't know how they worked.
The best developers hand optimized assembly for sub routines which they knew compilers were not good at, the rest of us sure didn't understand how any of it worked, but nonetheless felt the differences and chose with dollars and usage .
If you have enough tests at what point does AI rewriting software in a different language become close enough to ‘deterministic’? Maybe never, maybe not.