well this wasn't so strange really... 70-88 isn't the difference, if we check out the teams and see that both have 6*s and similar AvQs,
the game will check out the whole % of quality and dscard few players for the simulation, selecting 6-7 of each team to face each other creating a particular scenario with those players as main protagonists, so, thats is why, for example, a team full of 7*s VS a team with 50%-50% 7*s +1*s can have dispair results, losing the 2nd team 5-0 if the game select the 1*s to face the 7*, or winning 0-2 in opposite case.
Is a matter of how the game select the scenrios.