That 'person' (and I use that term lightly) would have been about as far from Sam as a vampire is of the person they used to be. Sure, memories, personality quirks, those would have been the same. And yeah, maybe Sam would have been 'happy' like that. But he wouldn't have been Sam. Not the Sam we all love and who he wants to be.
I guess that's what happens with lies, they make you doubt everything. Like, Sam lying to me made me question all of his feelings over the last few months. What we have now, we've had to rebuild from scratch because I couldn't separate the truth from the lies of what there was before. Like Sam doesn't know now how many of those in jokes and fries were because you liked him as a friend and how many were because you were grooming him to be what you wanted.