I can confirm that it works this way. Intended? Hard to say. It creates a difference to gold gifts, which only works for one recipient - and you can question that difference (both from balance and immersion). My guess it that having different "aid build projects" for different competitions is probably technically harder to code, so it was "solved" this way. It also has positive side effect, if there are multiple aid competitions running, but there end date is different - you don't lose ongoing efforts for the 1st ending one.