There's really not much of a limit at all for non-starchy vegatables. It is next to impossible to blow any macro-nutrient limits eating non-starchy vegetables.
Fruits are basically bags of sugar. So the limits on fruits boil down to the limits of sugars and overall carbohydrates per day. There are many variants of paleo type diets, but rarely does any recommend people excite 100-150 grams of carbohydrates. Those that do, actually recommend doing so via small amounts of rice or sweet potato to avoid the fructose.
And this is all because the vast amount of research followed by paleo folx centers around controlling the damaging effects of sugar and carbs in general.
Also depends on your weight loss plan. If you want to lose weight, particularly fast, its usually necessary to go very low carb. If you reached a maintenance point, there is room to play around with how much carbs (and therefore sugars) you can put into your diet.
But if someone starts off first on a supposed paleo diet, not really doing paleo but eating as many fruits as they want, then they won't learn how the diet really affects their body without the excess carbs, in order to best know the impact of adding them back in.
Recommendation is usually that people be strict for 30 days so there is a baseline understanding of the impact of the diet on the body, as well as forcing the body to change its metabolism, and add things back in from there.
However, people can do what they want, and people around here usually do, they just do it from a standpoint of experience and knowledge.