No what you have to do is understand the difference between what’s said in the show and how you’re interpreting it. I don’t think anybody in the show ever said there are no biological differences, all they said was there were no differences THEY COULD FIND. There’s a major scope difference there. Quite possibly had they had more than 3 doctors to handle 50,000 people they could have spent the time to do a full dissection and found the source of the glowing spine and then had a biological difference. But they only had 3 doctors to handle 50,000 people and 1 of them is a shrink and and another turned out to be a murderer so they don’t really have the time for full dissections, so they have FOUND no differences.
That’s the simple little reality in the show.
If you’ll notice 99% of what I’ve written is taking apart your assumption. That’s not labor explaining the show, that’s labor explaining your brain. The stuff in the show is simple, it’s all just one or two minor logical leaps away from stuff we know or theorize is possible today. All the other stuff is you assuming absolutes that have never once been stated in the show then complaining that those unstated absolutes are unsupported by events in the show. Since they never actually say there are no biological differences, then the fact that the glowing spine would seem to indicate some level of biological difference is not a contradiction. You assume since they could find a difference in whatever probably minor testing they’ve done equals no biological difference, but that’s YOUR assumption. Your assumptions make a lot of labor, but it’s fun labor (I actually enjoy deep analysis of shows), the show itself makes very little.
I only make 'assumptions' in the sense of working assumptions; a better phrase might be hypotheses or best explanations. I see something that doesn't quite add up and I try to come up with a best explanation, and if that best explanation still doesn't quite work, there's a problem. For example, my working assumption is that, because of that scene in the miniseries, Cylons actually do have spines that can glow, and I proceed from that point. But someone else (you?) mentioned the possibility that the 'glowing spine' was just for the TV viewers' benefit. I agree that's a possibility too! But it's a subpar explanation and just leads to a new critique. Another example is your explanation here, that the glowing spine results from something like two tiny 'enzyme sacs' that are nearly impossible to find - but that forces me to think that Cylon robots made their humanoids identical to humans in every way except for two tiny unfindable enzyme sacs whose only purpose is to make the spine glow during sex, which is even more stupid.
The point being that I'm not wedded to my 'assumptions' at all, it's just that if/when my 'assumption' (best explanation) is wrong, that's fine, but it tends to only raise new and more unresolvable questions. It's not that I think it's literally not possible for the glowing spine to be the result of what you describe, it's just that if I really thought 'unnoticeable enzyme sacs' were the best explanation, I'd have gone ahead and 'assumed' it, in which case my objection here would be how stupid it was for the writers to be telling us that the Cylons made their skinjobs identical to humans except for the enzyme sacs.
Finally, more generally I find it odd when I have a list of things, someone picks ONE item from the list (in your case the 'glowing spine'), ignoring the others, labors for a dozen posts to pick their chosen item apart, and then triumphantly declares all my points debunked. As if my entire critique against BSG was the glowing spine! This isn't even my main critique (which at this point centers on how little sense it makes for the final 4-out-of-5 to be suddenly, randomly Cylons).