It seems that the game does not consider the list that was input during the 30s period; it just goes by the list that was there before the match started and the other penalty takers are chosen by the game itself. No surprise to see players like DC, DMC and so on taking the penalties among the first 5 given that the game itself is poor in terms of choosing what should be appropriate (for example. how auto-subs or auto replacements are chosen; the game went as far as putting a GK as DMC for one of my matches this season when clearly other outfield players were available)
BTW, my team lost on the penalty shoot-out too (2:4).