I'm familiar with GAPS and follow some of the principles, like well cooked food, bone broth, and probiotic foods. I've just never done it start to finish. I think it makes a good fit with NSD, as the first few stages should limit how much starch makes it far enough down the GI tract to cause trouble.
With fruit and veg, zero starch is really hard to achieve. In the early days I aimed for a max of 2 grams per day (using www.cronometer.com
to check starch levels and iodine to verify). Some low starch veg or fruit might have some starch streaks, like veins, but did not cause me pain when I ate them. Presumably not enough starch to cause trouble. I did a lot of experimenting to see what I could/could not tolerate - one thing I've learned from this site is that people have very different levels of starch tolerance. (And they change over time - I can eat foods now that I couldn't before).
Having said that, zucchini always tested clear for me. Broccoli florets also were fine, though sometimes the tougher stems further down were starchy. I didn't eat cauliflower, but would expect it to behave the same way as broccoli. Cabbage and kale were iffy for me - their starch content can clearly vary, so I always tested, limited how much I ate, and cooked it really, really well in the hopes it would digest quickly.