So in my comparison between wine and water, the most the wine really did was to cause it to take another minute for me to reach "sticky." In my batch, I let it cure with the wine for ~18hrs or so, so I don't think that's the culprit here.
I looked at your mix and the first think I thought was "protein extraction from not mixing enough." That being said, you mix looked similar to
I-am-Chorizo
's, so I'm not sure about that. Here's a 3-way side by side with yours on the left:
View attachment 697900
You also didn't mention much fat-out, so I'm guessing that your hypothesis is mainly correct: the lean/fat ratio was off. The tenderloin you purchased needed some back fat or other pork fat to increase the fat content.
Did you estimate your fat by volume or by weight? If you used volume, then perhaps your actual ratio was more like 15% instead of 21%.
That being said, I've also had batches with low fat content and they still had a more consistent cut. So I wonder if you also had partial or incomplete extraction. I find I have to mix with wine about 20% longer than without, so maybe you mixed as you usually did, but it needed a little more...
My two cents, anyways. Your pictures look really good, and you're so much better at linking than me, haha. I'm glad your family enjoyed it, and that indicates to me that you were at least most of the way there with this sausage, I think.