I understand all of what your saying dude, tbh from a buyers point of view it's a safer bet to buy a RZ TT6 as meant to be by Toyota rather than a SZ with possible flaws. However, if all of the above quieries are well documented, as in proof of services on both engines, including a transplant with a fully serviced TT lump which has paperwork to show this, maybe the value will be better, however if I'm personally honest I'd rather have a RZ but insurance says no. But I did get a quote from Adrian flux for a TT transplant into my SZ on top of my renewal and it worked out cheaper than a quote on a already made up RZ stock... £200 more to be precise.
I think resell values are all down to how much a seller is willing to agree with, and a buyer is will to part with