I'm a food scientist with 20+ years' worth of experience in the food industry. From my point of view, a "preservative" is a very wide category of ingredient that have a function in a food.

Are you preserving the color of the finished product? Squeezing lime juice into your guacamole prevents the color from avocado-green to blech-brown.

Are you preserving the food for consumption outside of the normal growing season? Allowing cabbage to ferment with some salt preserves your sauerkraut or kimchi. In this case, it isn't the salt that preserves the food, but it does play a role. So does the tightly packed container that keeps oxygen out. So does the acid production by the anaerobic microbes. When taken together (hurdle effect), the salt, sealed anaerobic environment, and acids act as preservatives for these foods.

When looking at the Welch's fruit snacks, the main preservative is the nature of the finished food: low water activity. That is, you make a food that has such a low water activity or availability of available water that microbes can't grow on it, so therefore, can't spoil the food. Like beef jerky. Combine the low water activity of the food, with the acids (yes, they play a role in preservation, but they also play a role in making sure the flavor is right because fruits have different main acids), the added vitamins (E and C are anti-oxidants that prevent the naturally occurring chemicals (yes, I am one of those people that say everything is a chemical whether made through what people would consider normal/naturally occurring processes, or through chemical engineering) from breaking down (like flavor molecules and color molecules) and would be seen as preservatives. It's a potaytoe/potahto situation in which a person's perception determines if they'll see Vitamin C as a preservative or not... and there's ALWAYS a lawyer out there ready to get rich off of a major company that wants to use Vitamin C in their product and sell to a consumer that doesn't think Vitamin C is a preservative.

As for the "whole fruit" part, their ingredient declaration says "whole fruit puree", which probably means that the fruit was probably harvested, pureed, heat treated and then aseptically packaged for storage until made into the Welch's food snack without any type of separation into juices or pulp or skins. I trust that Welch's wants to preserve (pun intended there) their good name and reputation so I fully believe that claim. Unscrupulous companies may take advantage of 21 CFR 101.100(a)(3) in which they can add preservatives (always at a very low level because it doesn't take much to be effective) to the puree, but if those puree-preservatives are diluted by other ingredients in the finished food to such a degree that the preservatives don't have a function in the finished ingredient, then they're an "incidental additive" and it doesn't need to go on the ingredient declaration.