That’s a good point. Maybe you should be able to type “1e20” in scientific mode? It would make the calculator more feature full and prevent “losing” data if you copy/paste in the middle of a long calculation.
"e" in scientific mode is a shortcut for the "ln" function.
That said, I tested again, and once again copying "1e20" and pasting it into the Calculator works just fine. It's definitely not treating it the same as pressing each key separately. I'm testing on macOS 13.0.1.