Hmm that's an excellent questions. I played the scenario only having the dwarves be able to jump, i never really thought more about it since i just read it that way, but according to the "real rules" the goblins can surely jump as well, but does it make that big of a difference? When i played, the dwarves held most of the goblins at the bridge where they start (1 dwarf can hold a horde of goblins since he will only be fighting 2 at a time, given he wins the duel rolls). Having the best fighter hold i could have the other 2 jump across to fetch the baggage and kill the goblins present.
That's how my battle went at least
Edit//
Was curious, since you've played the second scenario i assume you've tried the first as well. How did that work out? i find it very hard for the dwarves to win this, tried 2-3 times and they just can't make it