Suggested donation value is just that. Suggested. Either you paid minimum price or above and gained ownership and have the game in your library - or not.
Think of it as buying the game on a discount. If you paid at all, you still have it purchased, even if the price changes. That is actually not hard to grasp. It only sounds complicated for all those pay what you want games that start at 0 amount. It does not count as a purchase if you download such a game without paying. But any amount at all does.
Should you have individually priced files, things get complicated. Mostly because there is no way to increase the paid amount later. Those files are completely separated from the rest of the purchase. You can only access them if you paid more than a fixed amount. They should completely overhaul this feature in favor of regular dlc. It confuses devs and buyers alike.