I see what you mean.
Wight was particularly confusing for me. I went from being extremely thin (100lbs.) two years ago to normal (130) and it appeared as if I was gaining weight especially due to gas and bloating when eating raw foods and juicing. If anything then the weight should have been interpreted as UNSTABLE which is pure Vata.
Instead of relying on a single snapshot of what we can observe in this particular moment we should look at the process, right?...
I noticed the Vata connection when reading this forum too. I see a lot of people with extreme Vata imbalances. I only realized it in myself when I started obsessing on my health too much. I can't meditate no more because the mind became extremely "aggressive" and wouldn't just shut up at all lately.
Another thing is that I always tried to stay away from heavy oily foods like nuts because of all the fat and because they would increase kapha. However almonds work great to control hypoglycemia which became so extreme that I couldn't leave the house. I've been munching on them for a week by now and I noticed that I actually look more muscular and lean instead of getting fat. My energy picked up and digestion improved. That's when I started to suspect that it could have been Vata problem all along and not Kapha that I was trying to reduce....
It seems so unlikely that these two doshas could be confused like that since they are nearly opposite but it AF is quite a unique condition in way where it is possible to make such mistake