In post #51 and in your original post #1, you show a single-ended input. Now, in post #59 you have changed it to differential input.
Those two different methods of input drive give the same outputs only if Rs = ∞, but that's not the case in the circuit of post #1.
It's true that the outputs with Rs = 200k are nearly the same as if Rs = ∞, but you wouldn't know that unless you performed an analysis for both cases, would you?
Yes, but in post #59 I already converted the original circuit into it's hybrid model... That's why those 2 voltage supplies show up with half of the value and with the polarity inverted!