Duck sauce, to me, is essentially hoisin thinned with something tangy. The stuff for your egg roll is sweet & sour. And I think of it as apricot.
The red sauce with the pork hunks is also sweet & sour, but it seems like it popped up with the Chinese buffets. The previous version, and the type at Mom & Pop Americanized Chinese restaurants, was the same as the egg roll stuff + pineapple and green pepper.