Good teams get upset in the playoffs all the time, both in WIS and in MLB.
That said, I think two additional things are worth noting:
1.) In WIS, it is not uncommon for a team's final W-L record to not be a good indication of its overall quality. For example, I routinely make it to the postseason in OL's with teams with 85-90 wins (and often these teams give up more runs than they score, sometimes by a substantial margin). Because I routinely rest players in interleague games, and once I think I've got a postseason berth locked up I rest players aggressively. My teams often have 20+ games started by mopup pitchers and scrub lineups. The point is their real talent level is probably more like a 100 or 105 in team, not 88-74.
2.) In real MLB you often see managers use strategies and tactics in the postseason, that they would never or rarely use in the regular season (think about the number of starters used in relief in key moments in the 2018 postseason). This is analogous to the Milacki strategy that ozomatli mentioned above. Something to think about...in WIS are there any other unique strategies that might be worth considering for the postseason? Are there any settings that you might want to change in the postseason? Without giving away too much, in my opinion the answer to both of these questions is a resounding yes.