You're right, I think I quickly went to the wrong thread. There are quite a few posts and images correlating Tau and Gundam.
But I don't think that there are no similarities: (Excuse the low quality recolor) I can see the difference, but the latter reminds me quite a bit of the former.
No, the thread you linked was originally about Gundam models standing in for Tau. There's just another link within the thread that links another thread where someone was looking to make Gundam conversions for Imperial Knights.
I still don't seem much resemblance between the two. Starting from top to bottom...
Feet and ankles are completely different. The proportions of the feet and "thighs" are completely different, too. How the hips are articulated are different. The XV02's joints are splayed out.
There's that little codpiece-like thing on both of them. That is a point of similarity.
The XV02's waist also slims way down. The Gundam's has some narrowing, but no where near to the same degree. The shoulders and chest look nothing alike. The red area of the chest where the Gundam pilot would exit does look similar to the red area on the XV02, but in the original coloring from the Tau codex, it does not appear as if the front has that concave slope that the Gundam does. The front of the battlesuit is likely flat and not angled.
The strongest resemblance between the two are the forearms and hands. Even so, it's not too close since the proportion of the arms to the rest of the body is very different.
Besides the idea that they're supposed to be humanoid, there's not too much to directly compare. You couldn't imagine dropping a Gundam mostly unmodified into a Tau army and not have it look conspicuous.