I think most of the pronounciation comes from whatever "Sotaques" Duolingo chooses to use for each translation. The d sounding like a j us used in places like Rio de Janeiro, where their general pronounciation of S sounds more like the european use is an s (sh sound). Other places in Brazil, up north i think, tend to use a hard D sound.
I believe (I'm not still really sure but..) that the use of the sound "j" when a word starts or even when it finishes with "D" is variable, same as it happens with the "t". You could pronounce /jisculpe/ or /desculpe/, because most of people who live in the south tend to use the J and the north ppl goes for D. It's called "Sotaque" here in Brasil. I'll ask some mates, good question! :D